1. SQL Statements and Structure

1.1 SQL Statements

1.1.1 Account Management SQL Commands

1.1.1.1 CREATE USER

Syntax

CREATE [OR REPLACE] USER [IF NOT EXISTS] 
 user_specification [,user_specification ...] 
  [REQUIRE {NONE | tls_option [[AND] tls_option ...] }]
  [WITH resource_option [resource_option ...] ]
  [lock_option] [password_option] 

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule  ...]

authentication_rule:
    authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

tls_option:
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

resource_option:
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

password_option:
  PASSWORD EXPIRE
  | PASSWORD EXPIRE DEFAULT
  | PASSWORD EXPIRE NEVER
  | PASSWORD EXPIRE INTERVAL N DAY

lock_option:
    ACCOUNT LOCK
  | ACCOUNT UNLOCK
}

Description

The CREATE USER statement creates new MariaDB accounts. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE USER creates a new row in mysql.user (until MariaDB 10.3 this is a table, from MariaDB 10.4 it's a view) or mysql.global_priv_table (from MariaDB 10.4) that has no privileges.

If any of the specified accounts, or any permissions for the specified accounts, already exist, then the server returns ERROR 1396 (HY000). If an error occurs, CREATE USER will still create the accounts that do not result in an error. Only one error is produced for all users which have not been created:

ERROR 1396 (HY000): 
  Operation CREATE USER failed for 'u1'@'%','u2'@'%'

CREATE USER, DROP USER, CREATE ROLE, and DROP ROLE all produce the same error code when they fail.

See Account Names below for details on how account names are specified.

OR REPLACE

If the optional OR REPLACE clause is used, it is basically a shortcut for:

DROP USER IF EXISTS name;
CREATE USER name ...;

For example:

CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test'

CREATE OR REPLACE USER foo2@test IDENTIFIED BY 'password';
Query OK, 0 rows affected (0.00 sec)

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified user already exists.

For example:

CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test'

CREATE USER IF NOT EXISTS foo2@test IDENTIFIED BY 'password';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------------+
| Level | Code | Message                                            |
+-------+------+----------------------------------------------------+
| Note  | 1973 | Can't create user 'foo2'@'test'; it already exists |
+-------+------+----------------------------------------------------+

Authentication Options

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored in the mysql.user/mysql.global_priv_table table.

For example, if our password is mariadb, then we can create the user with:

CREATE USER foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored in the mysql.user/mysql.global_priv_table table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)

And then we can create a user with the hash:

CREATE USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

CREATE USER foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

CREATE USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

MariaDB starting with 10.4.0

The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');
MariaDB starting with 10.4.3

One can specify many authentication plugins, they all work as alternatives ways of authenticating a user:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket;

By default, when you create a user without specifying an authentication plugin, MariaDB uses the mysql_native_password plugin.

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can create a user account that requires these TLS options with the following:

CREATE USER 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

Here is an example showing how to create a user with resource limits:

CREATE USER 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 10
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

Account Names

Account names have both a user name component and a host name component, and are specified as 'user_name'@'host_name'.

The user name and host name may be unquoted, quoted as strings using double quotes (") or single quotes ('), or quoted as identifiers using backticks (`). You must use quotes when using special characters (such as a hyphen) or wildcard characters. If you quote, you must quote the user name and host name separately (for example 'user_name'@'host_name').

Host Name Component

If the host name is not provided, it is assumed to be '%'.

Host names may contain the wildcard characters % and _. They are matched as if by the LIKE clause. If you need to use a wildcard character literally (for example, to match a domain name with an underscore), prefix the character with a backslash. See LIKE for more information on escaping wildcard characters.

Host name matches are case-insensitive. Host names can match either domain names or IP addresses. Use 'localhost' as the host name to allow only local client connections.

You can use a netmask to match a range of IP addresses using 'base_ip/netmask' as the host name. A user with an IP address ip_addr will be allowed to connect if the following condition is true:

ip_addr & netmask = base_ip

For example, given a user:

CREATE USER 'maria'@'247.150.130.0/255.255.255.0';

the IP addresses satisfying this condition range from 247.150.130.0 to 247.150.130.255.

Using 255.255.255.255 is equivalent to not using a netmask at all. Netmasks cannot be used for IPv6 addresses.

Note that the credentials added when creating a user with the '%' wildcard host will not grant access in all cases. For example, some systems come with an anonymous localhost user, and when connecting from localhost this will take precedence.

Before MariaDB 10.6, the host name component could be up to 60 characters in length. Starting from MariaDB 10.6, it can be up to 255 characters.

User Name Component

User names must match exactly, including case. A user name that is empty is known as an anonymous account and is allowed to match a login attempt with any user name component. These are described more in the next section.

For valid identifiers to use as user names, see Identifier Names.

It is possible for more than one account to match when a user connects. MariaDB selects the first matching account after sorting according to the following criteria:

  • Accounts with an exact host name are sorted before accounts using a wildcard in the host name. Host names using a netmask are considered to be exact for sorting.
  • Accounts with a wildcard in the host name are sorted according to the position of the first wildcard character. Those with a wildcard character later in the host name sort before those with a wildcard character earlier in the host name.
  • Accounts with a non-empty user name sort before accounts with an empty user name.
  • Accounts with an empty user name are sorted last. As mentioned previously, these are known as anonymous accounts. These are described more in the next section.

The following table shows a list of example account as sorted by these criteria:

+---------+-------------+
| User    | Host        |
+---------+-------------+
| joffrey | 192.168.0.3 |
|         | 192.168.0.% |
| joffrey | 192.168.%   |
|         | 192.168.%   |
+---------+-------------+

Once connected, you only have the privileges granted to the account that matched, not all accounts that could have matched. For example, consider the following commands:

CREATE USER 'joffrey'@'192.168.0.3';
CREATE USER 'joffrey'@'%';
GRANT SELECT ON test.t1 to 'joffrey'@'192.168.0.3';
GRANT SELECT ON test.t2 to 'joffrey'@'%';

If you connect as joffrey from 192.168.0.3, you will have the SELECT privilege on the table test.t1, but not on the table test.t2. If you connect as joffrey from any other IP address, you will have the SELECT privilege on the table test.t2, but not on the table test.t1.

Usernames can be up to 80 characters long before 10.6 and starting from 10.6 it can be 128 characters long.

Anonymous Accounts

Anonymous accounts are accounts where the user name portion of the account name is empty. These accounts act as special catch-all accounts. If a user attempts to log into the system from a host, and an anonymous account exists with a host name portion that matches the user's host, then the user will log in as the anonymous account if there is no more specific account match for the user name that the user entered.

For example, here are some anonymous accounts:

CREATE USER ''@'localhost';
CREATE USER ''@'192.168.0.3';

Fixing a Legacy Default Anonymous Account

On some systems, the mysql.db table has some entries for the ''@'%' anonymous account by default. Unfortunately, there is no matching entry in the mysql.user/mysql.global_priv_table table, which means that this anonymous account doesn't exactly exist, but it does have privileges--usually on the default test database created by mysql_install_db. These account-less privileges are a legacy that is leftover from a time when MySQL's privilege system was less advanced.

This situation means that you will run into errors if you try to create a ''@'%' account. For example:

CREATE USER ''@'%';
ERROR 1396 (HY000): Operation CREATE USER failed for ''@'%'

The fix is to DELETE the row in the mysql.db table and then execute FLUSH PRIVILEGES:

DELETE FROM mysql.db WHERE User='' AND Host='%';
FLUSH PRIVILEGES;

And then the account can be created:

CREATE USER ''@'%';
Query OK, 0 rows affected (0.01 sec)

See MDEV-13486 for more information.

Password Expiry

MariaDB starting with 10.4.3

Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;

See User Password Expiry for more details.

Account Locking

MariaDB starting with 10.4.2

Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example:

CREATE USER 'marijn'@'localhost' ACCOUNT LOCK;

See Account Locking for more details.

From MariaDB 10.4.7 and MariaDB 10.5.8, the lock_option and password_option clauses can occur in either order.

See Also

1.1.1.2 ALTER USER

MariaDB starting with 10.2.0

The ALTER USER statement was introduced in MariaDB 10.2.0.

Syntax

ALTER USER [IF EXISTS] 
 user_specification [,user_specification] ...
  [REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
  [WITH resource_option [resource_option] ...]
  [lock_option] [password_option] 

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule] ... 
 
authentication_rule:
  authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

tls_option
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

resource_option
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

password_option:
  PASSWORD EXPIRE
  | PASSWORD EXPIRE DEFAULT
  | PASSWORD EXPIRE NEVER
  | PASSWORD EXPIRE INTERVAL N DAY

lock_option:
    ACCOUNT LOCK
  | ACCOUNT UNLOCK
}

Description

The ALTER USER statement modifies existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. The global SUPER privilege is also required if the read_only system variable is enabled.

If any of the specified user accounts do not yet exist, an error results. If an error occurs, ALTER USER will still modify the accounts that do not result in an error. Only one error is produced for all users which have not been modified.

IF EXISTS

When the IF EXISTS clause is used, MariaDB will return a warning instead of an error for each specified user that does not exist.

Account Names

For ALTER USER statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified.

CURRENT_USER or CURRENT_USER() can also be used to alter the account logged into the current session. For example, to change the current user's password to mariadb:

ALTER USER CURRENT_USER() IDENTIFIED BY 'mariadb';

Authentication Options

MariaDB starting with 10.4

From MariaDB 10.4, it is possible to use more than one authentication plugin for each user account. For example, this can be useful to slowly migrate users to the more secure ed25519 authentication plugin over time, while allowing the old mysql_native_password authentication plugin as an alternative for the transitional period. See Authentication from MariaDB 10.4 for more.

When running ALTER USER, not specifying an authentication option in the IDENTIFIED VIA clause will remove that authentication method. (However this was not the case before MariaDB 10.4.13, see MDEV-21928)

For example, a user is created with the ability to authenticate via both a password and unix_socket:

CREATE USER 'bob'@'localhost' 
  IDENTIFIED VIA mysql_native_password USING PASSWORD('pwd') 
  OR unix_socket;

SHOW CREATE USER 'bob'@'localhost'\G
*************************** 1. row ***************************
CREATE USER for bob@localhost: CREATE USER `bob`@`localhost` 
  IDENTIFIED VIA mysql_native_password USING '*975B2CD4FF9AE554FE8AD33168FBFC326D2021DD' 
  OR unix_socket

If the user's password is updated, but unix_socket authentication is not specified in the IDENTIFIED VIA clause, unix_socket authentication will no longer be permitted.

ALTER USER 'bob'@'localhost' IDENTIFIED VIA mysql_native_password USING PASSWORD('pwd2');

SHOW CREATE USER 'bob'@'localhost'\G
*************************** 1. row ***************************
CREATE USER for bob@localhost: CREATE USER `bob`@`localhost` 
  IDENTIFIED BY PASSWORD '*38366FDA01695B6A5A9DD4E428D9FB8F7EB75512'

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table.

For example, if our password is mariadb, then we can set the account's password with:

ALTER USER foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD#function. It will be stored to the mysql.user table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+

And then we can set an account's password with the hash:

ALTER USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

ALTER USER foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

ALTER USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

In MariaDB 10.4 and later, the USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

ALTER USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can alter a user account to require these TLS options with the following:

ALTER USER 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

Here is an example showing how to set an account's resource limits:

ALTER USER 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 10
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

Password Expiry

MariaDB starting with 10.4.3

Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example:

ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;

See User Password Expiry for more details.

Account Locking

MariaDB starting with 10.4.2

Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example:

ALTER USER 'marijn'@'localhost' ACCOUNT LOCK;

See Account Locking for more details.

From MariaDB 10.4.7 and MariaDB 10.5.8, the lock_option and password_option clauses can occur in either order.

See Also

1.1.1.3 DROP USER

Syntax

DROP USER [IF EXISTS] user_name [, user_name] ...

Description

The DROP USER statement removes one or more MariaDB accounts. It removes privilege rows for the account from all grant tables. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see CREATE USER.

Note that, if you specify an account that is currently connected, it will not be deleted until the connection is closed. The connection will not be automatically closed.

If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP USER will still drop the accounts that do not result in an error. Only one error is produced for all users which have not been dropped:

ERROR 1396 (HY000): Operation DROP USER failed for 'u1'@'%','u2'@'%'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the user does not exist.

Examples

DROP USER bob;

IF EXISTS:

DROP USER bob;
ERROR 1396 (HY000): Operation DROP USER failed for 'bob'@'%'

DROP USER IF EXISTS bob;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message                                     |
+-------+------+---------------------------------------------+
| Note  | 1974 | Can't drop user 'bob'@'%'; it doesn't exist |
+-------+------+---------------------------------------------+

See Also

1.1.1.4 GRANT

Syntax

GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    TO user_specification [ user_options ...]

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule  ...]

authentication_rule:
    authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

GRANT PROXY ON username
    TO user_specification [, user_specification ...]
    [WITH GRANT OPTION]

GRANT rolename TO grantee [, grantee ...]
    [WITH ADMIN OPTION]

grantee:
    rolename
    username [authentication_option]

user_options:
    [REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
    [WITH with_option [with_option] ...]

object_type:
    TABLE
  | FUNCTION
  | PROCEDURE
  | PACKAGE

priv_level:
    *
  | *.*
  | db_name.*
  | db_name.tbl_name
  | tbl_name
  | db_name.routine_name

with_option:
    GRANT OPTION
  | resource_option

resource_option:
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

tls_option:
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

Description

The GRANT statement allows you to grant privileges or roles to accounts. To use GRANT, you must have the GRANT OPTION privilege, and you must have the privileges that you are granting.

Use the REVOKE statement to revoke privileges granted with the GRANT statement.

Use the SHOW GRANTS statement to determine what privileges an account has.

Account Names

For GRANT statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified.

Implicit Account Creation

The GRANT statement also allows you to implicitly create accounts in some cases.

If the account does not yet exist, then GRANT can implicitly create it. To implicitly create an account with GRANT, a user is required to have the same privileges that would be required to explicitly create the account with the CREATE USER statement.

If the NO_AUTO_CREATE_USER SQL_MODE is set, then accounts can only be created if authentication information is specified, or with a CREATE USER statement. If no authentication information is provided, GRANT will produce an error when the specified account does not exist, for example:

show variables like '%sql_mode%' ;
+---------------+--------------------------------------------+
| Variable_name | Value                                      |
+---------------+--------------------------------------------+
| sql_mode      | NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+--------------------------------------------+

GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED BY '';
ERROR 1133 (28000): Can't find any matching row in the user table

GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED VIA PAM using 'mariadb' require ssl ;
Query OK, 0 rows affected (0.00 sec)
 
select host, user from mysql.user where user='user123' ;

+------+----------+
| host | user     |
+------+----------+
| %    | user123 |
+------+----------+

Privilege Levels

Privileges can be set globally, for an entire database, for a table or routine, or for individual columns in a table. Certain privileges can only be set at certain levels.

  • Global privileges priv_type are granted using *.* for priv_level. Global privileges include privileges to administer the database and manage user accounts, as well as privileges for all tables, functions, and procedures. Global privileges are stored in the mysql.user table.
  • Database privileges priv_type are granted using db_name.* for priv_level, or using just * to use default database. Database privileges include privileges to create tables and functions, as well as privileges for all tables, functions, and procedures in the database. Database privileges are stored in the mysql.db table.
  • Table privileges priv_type are granted using db_name.tbl_name for priv_level, or using just tbl_name to specify a table in the default database. The TABLE keyword is optional. Table privileges include the ability to select and change data in the table. Certain table privileges can be granted for individual columns.
  • Column privileges priv_type are granted by specifying a table for priv_level and providing a column list after the privilege type. They allow you to control exactly which columns in a table users can select and change.
  • Function privileges priv_type are granted using FUNCTION db_name.routine_name for priv_level, or using just FUNCTION routine_name to specify a function in the default database.
  • Procedure privileges priv_type are granted using PROCEDURE db_name.routine_name for priv_level, or using just PROCEDURE routine_name to specify a procedure in the default database.

The USAGE Privilege

The USAGE privilege grants no real privileges. The SHOW GRANTS statement will show a global USAGE privilege for a newly-created user. You can use USAGE with the GRANT statement to change options like GRANT OPTION and MAX_USER_CONNECTIONS without changing any account privileges.

The ALL PRIVILEGES Privilege

The ALL PRIVILEGES privilege grants all available privileges. Granting all privileges only affects the given privilege level. For example, granting all privileges on a table does not grant any privileges on the database or globally.

Using ALL PRIVILEGES does not grant the special GRANT OPTION privilege.

You can use ALL instead of ALL PRIVILEGES.

The GRANT OPTION Privilege

Use the WITH GRANT OPTION clause to give users the ability to grant privileges to other users at the given privilege level. Users with the GRANT OPTION privilege can only grant privileges they have. They cannot grant privileges at a higher privilege level than they have the GRANT OPTION privilege.

The GRANT OPTION privilege cannot be set for individual columns. If you use WITH GRANT OPTION when specifying column privileges, the GRANT OPTION privilege will be granted for the entire table.

Using the WITH GRANT OPTION clause is equivalent to listing GRANT OPTION as a privilege.

Global Privileges

The following table lists the privileges that can be granted globally. You can also grant all database, table, and function privileges globally. When granted globally, these privileges apply to all databases, tables, or functions, including those created later.

To set a global privilege, use *.* for priv_level.

BINLOG ADMIN

Enables administration of the binary log, including the PURGE BINARY LOGS statement and setting the binlog_annotate_row_events, binlog_cache_size, binlog_commit_wait_count, binlog_commit_wait_usec, binlog_direct_non_transactional_updates, binlog_expire_logs_seconds, binlog_file_cache_size, binlog_format, binlog_row_image, binlog_row_metadata, binlog_stmt_cache_size, expire_logs_days, log_bin_compress, log_bin_compress_min_len, log_bin_trust_function_creators, max_binlog_cache_size, max_binlog_size, max_binlog_stmt_cache_size, sql_log_bin and sync_binlog system variables. Added in MariaDB 10.5.2.

BINLOG MONITOR

New name for REPLICATION CLIENT from MariaDB 10.5.2, (REPLICATION CLIENT still supported as an alias for compatibility purposes). Permits running SHOW commands related to the binary log, in particular the SHOW BINLOG STATUS, SHOW REPLICA STATUS and SHOW BINARY LOGS statements.

BINLOG REPLAY

Enables replaying the binary log with the BINLOG statement (generated by mariadb-binlog), executing SET timestamp when secure_timestamp is set to replication, and setting the session values of system variables usually included in BINLOG output, in particular gtid_domain_id, gtid_seq_no, pseudo_thread_id and server_id. Added in MariaDB 10.5.2

CONNECTION ADMIN

Enables administering connection resource limit options. This includes ignoring the limits specified by max_connections, max_user_connections and max_password_errors, not executing the statements specified in init_connect, killing connections and queries owned by other users as well as setting the following connection-related system variables: connect_timeout, disconnect_on_expired_password, extra_max_connections, init_connect, max_connections, max_connect_errors, max_password_errors, proxy_protocol_networks, secure_auth, slow_launch_time, thread_pool_exact_stats, thread_pool_dedicated_listener, thread_pool_idle_timeout, thread_pool_max_threads, thread_pool_min_threads, thread_pool_mode, thread_pool_oversubscribe, thread_pool_prio_kickup_timer, thread_pool_priority, thread_pool_size, thread_pool_stall_limit. Added in MariaDB 10.5.2.

CREATE USER

Create a user using the CREATE USER statement, or implicitly create a user with the GRANT statement.

FEDERATED ADMIN

Execute CREATE SERVER, ALTER SERVER, and DROP SERVER statements. Added in MariaDB 10.5.2.

FILE

Read and write files on the server, using statements like LOAD DATA INFILE or functions like LOAD_FILE(). Also needed to create CONNECT outward tables. MariaDB server must have the permissions to access those files.

GRANT OPTION

Grant global privileges. You can only grant privileges that you have.

PROCESS

Show information about the active processes, for example via SHOW PROCESSLIST or mysqladmin processlist. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using).

READ_ONLY ADMIN

User can set the read_only system variable and allows the user to perform write operations, even when the read_only option is active. Added in MariaDB 10.5.2.

RELOAD

Execute FLUSH statements or equivalent mariadb-admin/mysqladmin commands.

REPLICATION CLIENT

Execute SHOW MASTER STATUS, SHOW SLAVE STATUS and SHOW BINARY LOGS informative statements. Renamed to BINLOG MONITOR in MariaDB 10.5.2 (but still supported as an alias for compatibility reasons).

REPLICATION MASTER ADMIN

Permits administration of primary servers, including the SHOW REPLICA HOSTS statement, and setting the gtid_binlog_state, gtid_domain_id, master_verify_checksum and server_id system variables. Added in MariaDB 10.5.2.

REPLICA MONITOR

Permit SHOW REPLICA STATUS and SHOW RELAYLOG EVENTS. From MariaDB 10.5.9.

When a user would upgrade from an older major release to a MariaDB 10.5 minor release prior to MariaDB 10.5.9, certain user accounts would lose capabilities. For example, a user account that had the REPLICATION CLIENT privilege in older major releases could run SHOW REPLICA STATUS, but after upgrading to a MariaDB 10.5 minor release prior to MariaDB 10.5.9, they could no longer run SHOW REPLICA STATUS, because that statement was changed to require the REPLICATION REPLICA ADMIN privilege.

This issue is fixed in MariaDB 10.5.9 with this new privilege, which now grants the user the ability to execute SHOW [ALL] (SLAVE | REPLICA) STATUS.

When a database is upgraded from an older major release to MariaDB Server 10.5.9 or later, any user accounts with the REPLICATION CLIENT or REPLICATION SLAVE privileges will automatically be granted the new REPLICA MONITOR privilege. The privilege fix occurs when the server is started up, not when mariadb-upgrade is performed.

However, when a database is upgraded from an early 10.5 minor release to 10.5.9 and later, the user will have to fix any user account privileges manually.

REPLICATION REPLICA

Synonym for REPLICATION SLAVE. From MariaDB 10.5.1.

REPLICATION SLAVE

Accounts used by replica servers on the primary need this privilege. This is needed to get the updates made on the master. From MariaDB 10.5.1, REPLICATION REPLICA is an alias for REPLICATION SLAVE.

REPLICATION SLAVE ADMIN

Permits administering replica servers, including START REPLICA/SLAVE, STOP REPLICA/SLAVE, CHANGE MASTER, SHOW REPLICA/SLAVE STATUS, SHOW RELAYLOG EVENTS statements, replaying the binary log with the BINLOG statement (generated by mariadb-binlog), and setting the gtid_cleanup_batch_size, gtid_ignore_duplicates, gtid_pos_auto_engines, gtid_slave_pos, gtid_strict_mode, init_slave, read_binlog_speed_limit, relay_log_purge, relay_log_recovery, replicate_do_db, replicate_do_table, replicate_events_marked_for_skip, replicate_ignore_db, replicate_ignore_table, replicate_wild_do_table, replicate_wild_ignore_table, slave_compressed_protocol, slave_ddl_exec_mode, slave_domain_parallel_threads, slave_exec_mode, slave_max_allowed_packet, slave_net_timeout, slave_parallel_max_queued, slave_parallel_mode, slave_parallel_threads, slave_parallel_workers, slave_run_triggers_for_rbr, slave_sql_verify_checksum, slave_transaction_retry_interval, slave_type_conversions, sync_master_info, sync_relay_log and sync_relay_log_info system variables. Added in MariaDB 10.5.2.

SET USER

Enables setting the DEFINER when creating triggers, views, stored functions and stored procedures. Added in MariaDB 10.5.2.

SHOW DATABASES

List all databases using the SHOW DATABASES statement. Without the SHOW DATABASES privilege, you can still issue the SHOW DATABASES statement, but it will only list databases containing tables on which you have privileges.

SHUTDOWN

Shut down the server using SHUTDOWN or the mysqladmin shutdown command.

SUPER

Execute superuser statements: CHANGE MASTER TO, KILL (users who do not have this privilege can only KILL their own threads), PURGE LOGS, SET global system variables, or the mysqladmin debug command. Also, this permission allows the user to write data even if the read_only startup option is set, enable or disable logging, enable or disable replication on replica, specify a DEFINER for statements that support that clause, connect once after reaching the MAX_CONNECTIONS. If a statement has been specified for the init-connect mysqld option, that command will not be executed when a user with SUPER privileges connects to the server.

The SUPER privilege has been split into multiple smaller privileges from MariaDB 10.5.2 to allow for more fine-grained privileges, although it remains an alias for these smaller privileges.

Database Privileges

The following table lists the privileges that can be granted at the database level. You can also grant all table and function privileges at the database level. Table and function privileges on a database apply to all tables or functions in that database, including those created later.

To set a privilege for a database, specify the database using db_name.* for priv_level, or just use * to specify the default database.

PrivilegeDescription
CREATECreate a database using the CREATE DATABASE statement, when the privilege is granted for a database. You can grant the CREATE privilege on databases that do not yet exist. This also grants the CREATE privilege on all tables in the database.
CREATE ROUTINECreate Stored Programs using the CREATE PROCEDURE and CREATE FUNCTION statements.
CREATE TEMPORARY TABLESCreate temporary tables with the CREATE TEMPORARY TABLE statement. This privilege enable writing and dropping those temporary tables
DROPDrop a database using the DROP DATABASE statement, when the privilege is granted for a database. This also grants the DROP privilege on all tables in the database.
EVENTCreate, drop and alter EVENTs.
GRANT OPTIONGrant database privileges. You can only grant privileges that you have.
LOCK TABLESAcquire explicit locks using the LOCK TABLES statement; you also need to have the SELECT privilege on a table, in order to lock it.

Table Privileges

PrivilegeDescription
ALTERChange the structure of an existing table using the ALTER TABLE statement.
CREATECreate a table using the CREATE TABLE statement. You can grant the CREATE privilege on tables that do not yet exist.
CREATE VIEWCreate a view using the CREATE_VIEW statement.
DELETERemove rows from a table using the DELETE statement.
DELETE HISTORYRemove historical rows from a table using the DELETE HISTORY statement. Displays as DELETE VERSIONING ROWS when running SHOW GRANTS until MariaDB 10.3.15 and until MariaDB 10.4.5 (MDEV-17655), or when running SHOW PRIVILEGES until MariaDB 10.5.2, MariaDB 10.4.13 and MariaDB 10.3.23 (MDEV-20382). From MariaDB 10.3.4. From MariaDB 10.3.5, if a user has the SUPER privilege but not this privilege, running mysql_upgrade will grant this privilege as well.
DROPDrop a table using the DROP TABLE statement or a view using the DROP VIEW statement. Also required to execute the TRUNCATE TABLE statement.
GRANT OPTIONGrant table privileges. You can only grant privileges that you have.
INDEXCreate an index on a table using the CREATE INDEX statement. Without the INDEX privilege, you can still create indexes when creating a table using the CREATE TABLE statement if the you have the CREATE privilege, and you can create indexes using the ALTER TABLE statement if you have the ALTER privilege.
INSERTAdd rows to a table using the INSERT statement. The INSERT privilege can also be set on individual columns; see Column Privileges below for details.
REFERENCESUnused.
SELECTRead data from a table using the SELECT statement. The SELECT privilege can also be set on individual columns; see Column Privileges below for details.
SHOW VIEWShow the CREATE VIEW statement to create a view using the SHOW CREATE VIEW statement.
TRIGGERExecute triggers associated to tables you update, execute the CREATE TRIGGER and DROP TRIGGER statements. You will still be able to see triggers.
UPDATEUpdate existing rows in a table using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause. The UPDATE privilege can also be set on individual columns; see Column Privileges below for details.

Column Privileges

Some table privileges can be set for individual columns of a table. To use column privileges, specify the table explicitly and provide a list of column names after the privilege type. For example, the following statement would allow the user to read the names and positions of employees, but not other information from the same table, such as salaries.

GRANT SELECT (name, position) on Employee to 'jeffrey'@'localhost';
PrivilegeDescription
INSERT (column_list)Add rows specifying values in columns using the INSERT statement. If you only have column-level INSERT privileges, you must specify the columns you are setting in the INSERT statement. All other columns will be set to their default values, or NULL.
REFERENCES (column_list)Unused.
SELECT (column_list)Read values in columns using the SELECT statement. You cannot access or query any columns for which you do not have SELECT privileges, including in WHERE, ON, GROUP BY, and ORDER BY clauses.
UPDATE (column_list)Update values in columns of existing rows using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause.

Function Privileges

PrivilegeDescription
ALTER ROUTINEChange the characteristics of a stored function using the ALTER FUNCTION statement.
EXECUTEUse a stored function. You need SELECT privileges for any tables or columns accessed by the function.
GRANT OPTIONGrant function privileges. You can only grant privileges that you have.

Procedure Privileges

PrivilegeDescription
ALTER ROUTINEChange the characteristics of a stored procedure using the ALTER PROCEDURE statement.
EXECUTEExecute a stored procedure using the CALL statement. The privilege to call a procedure may allow you to perform actions you wouldn't otherwise be able to do, such as insert rows into a table.
GRANT OPTIONGrant procedure privileges. You can only grant privileges that you have.

Proxy Privileges

PrivilegeDescription
PROXYPermits one user to be a proxy for another.

The PROXY privilege allows one user to proxy as another user, which means their privileges change to that of the proxy user, and the CURRENT_USER() function returns the user name of the proxy user.

The PROXY privilege only works with authentication plugins that support it. The default mysql_native_password authentication plugin does not support proxy users.

The pam authentication plugin is the only plugin included with MariaDB that currently supports proxy users. The PROXY privilege is commonly used with the pam authentication plugin to enable user and group mapping with PAM.

For example, to grant the PROXY privilege to an anonymous account that authenticates with the pam authentication plugin, you could execute the following:

CREATE USER 'dba'@'%' IDENTIFIED BY 'strongpassword';
GRANT ALL PRIVILEGES ON *.* TO 'dba'@'%' ;

CREATE USER ''@'%' IDENTIFIED VIA pam USING 'mariadb';
GRANT PROXY ON 'dba'@'%' TO ''@'%';

A user account can only grant the PROXY privilege for a specific user account if the granter also has the PROXY privilege for that specific user account, and if that privilege is defined WITH GRANT OPTION. For example, the following example fails because the granter does not have the PROXY privilege for that specific user account at all:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                            |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
+-----------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';
ERROR 1698 (28000): Access denied for user 'alice'@'localhost'

And the following example fails because the granter does have the PROXY privilege for that specific user account, but it is not defined WITH GRANT OPTION:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                            |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
| GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost'                                                               |
+-----------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';
ERROR 1698 (28000): Access denied for user 'alice'@'localhost'

But the following example succeeds because the granter does have the PROXY privilege for that specific user account, and it is defined WITH GRANT OPTION:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                                              |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION |
| GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost' WITH GRANT OPTION                                                               |
+-----------------------------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';

A user account can grant the PROXY privilege for any other user account if the granter has the PROXY privilege for the ''@'%' anonymous user account, like this:

GRANT PROXY ON ''@'%' TO 'dba'@'localhost' WITH GRANT OPTION;

For example, the following example succeeds because the user can grant the PROXY privilege for any other user account:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                                              |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION |
| GRANT PROXY ON ''@'%' TO 'alice'@'localhost' WITH GRANT OPTION                                                                          |
+-----------------------------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'app1_dba'@'localhost' TO 'bob'@'localhost';
Query OK, 0 rows affected (0.004 sec)

GRANT PROXY ON 'app2_dba'@'localhost' TO 'carol'@'localhost';
Query OK, 0 rows affected (0.004 sec)

The default root user accounts created by mysql_install_db have this privilege. For example:

GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION;
GRANT PROXY ON ''@'%' TO 'root'@'localhost' WITH GRANT OPTION;

This allows the default root user accounts to grant the PROXY privilege for any other user account, and it also allows the default root user accounts to grant others the privilege to do the same.

Authentication Options

The authentication options for the GRANT statement are the same as those for the CREATE USER statement.

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table.

For example, if our password is mariadb, then we can create the user with:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)

And then we can create a user with the hash:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

MariaDB starting with 10.4.0

The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');
MariaDB starting with 10.4.3

One can specify many authentication plugins, they all work as alternatives ways of authenticating a user:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket;

By default, when you create a user without specifying an authentication plugin, MariaDB uses the mysql_native_password plugin.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

To set resource limits for an account, if you do not want to change that account's privileges, you can issue a GRANT statement with the USAGE privilege, which has no meaning. The statement can name some or all limit types, in any order.

Here is an example showing how to set resource limits:

GRANT USAGE ON *.* TO 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 0
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Users with the CONNECTION ADMIN privilege (in MariaDB 10.5.2 and later) or the SUPER privilege are not restricted by max_user_connections, max_connections, or max_password_errors.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can create a user account that requires these TLS options with the following:

GRANT USAGE ON *.* TO 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Roles

Syntax

GRANT role TO grantee [, grantee ... ]
[ WITH ADMIN OPTION ]

grantee:
    rolename
    username [authentication_option]

The GRANT statement is also used to grant the use a role to one or more users or other roles. In order to be able to grant a role, the grantor doing so must have permission to do so (see WITH ADMIN in the CREATE ROLE article).

Specifying the WITH ADMIN OPTION permits the grantee to in turn grant the role to another.

For example, the following commands show how to grant the same role to a couple different users.

GRANT journalist TO hulda;

GRANT journalist TO berengar WITH ADMIN OPTION;

If a user has been granted a role, they do not automatically obtain all permissions associated with that role. These permissions are only in use when the user activates the role with the SET ROLE statement.

Grant Examples

Granting Root-like Privileges

You can create a user that has privileges similar to the default root accounts by executing the following:

CREATE USER 'alexander'@'localhost';
GRANT ALL PRIVILEGES ON  *.* to 'alexander'@'localhost' WITH GRANT OPTION;

See Also

1.1.1.5 RENAME USER

Syntax

RENAME USER old_user TO new_user
    [, old_user TO new_user] ...

Description

The RENAME USER statement renames existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used.

If any of the old user accounts do not exist or any of the new user accounts already exist, ERROR 1396 (HY000) results. If an error occurs, RENAME USER will still rename the accounts that do not result in an error.

Examples

CREATE USER 'donald', 'mickey';
RENAME USER 'donald' TO 'duck'@'localhost', 'mickey' TO 'mouse'@'localhost';

1.1.1.6 REVOKE

Privileges

Syntax

REVOKE 
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    FROM user [, user] ...

REVOKE ALL PRIVILEGES, GRANT OPTION
    FROM user [, user] ...

Description

The REVOKE statement enables system administrators to revoke privileges (or roles - see section below) from MariaDB accounts. Each account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For details on the levels at which privileges exist, the allowable priv_type and priv_level values, and the syntax for specifying users and passwords, see GRANT.

To use the first REVOKE syntax, you must have the GRANT OPTION privilege, and you must have the privileges that you are revoking.

To revoke all privileges, use the second syntax, which drops all global, database, table, column, and routine privileges for the named user or users:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

To use this REVOKE syntax, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. See GRANT.

Examples

REVOKE SUPER ON *.* FROM 'alexander'@'localhost';

Roles

Syntax

REVOKE role  [, role ...]
    FROM grantee [, grantee2 ... ]

REVOKE ADMIN OPTION FOR role FROM grantee [, grantee2]

Description

REVOKE is also used to remove a role from a user or another role that it's previously been assigned to. If a role has previously been set as a default role, REVOKE does not remove the record of the default role from the mysql.user table. If the role is subsequently granted again, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this.

Before MariaDB 10.1.13, the REVOKE role statement was not permitted in prepared statements.

Example

REVOKE journalist FROM hulda

1.1.1.7 SET PASSWORD

Syntax

SET PASSWORD [FOR user] =
    {
        PASSWORD('some password')
      | OLD_PASSWORD('some password')
      | 'encrypted password'
    }

Description

The SET PASSWORD statement assigns a password to an existing MariaDB user account.

If the password is specified using the PASSWORD() or OLD_PASSWORD() function, the literal text of the password should be given. If the password is specified without using either function, the password should be the already-encrypted password value as returned by PASSWORD().

OLD_PASSWORD() should only be used if your MariaDB/MySQL clients are very old (< 4.0.0).

With no FOR clause, this statement sets the password for the current user. Any client that has connected to the server using a non-anonymous account can change the password for that account.

With a FOR clause, this statement sets the password for a specific account on the current server host. Only clients that have the UPDATE privilege for the mysql database can do this. The user value should be given in user_name@host_name format, where user_name and host_name are exactly as they are listed in the User and Host columns of the mysql.user table entry.

The argument to PASSWORD() and the password given to MariaDB clients can be of arbitrary length.

Authentication Plugin Support

MariaDB starting with 10.4

In MariaDB 10.4 and later, SET PASSWORD (with or without PASSWORD()) works for accounts authenticated via any authentication plugin that supports passwords stored in the mysql.global_priv table.

The ed25519, mysql_native_password, and mysql_old_password authentication plugins store passwords in the mysql.global_priv table.

If you run SET PASSWORD on an account that authenticates with one of these authentication plugins that stores passwords in the mysql.global_priv table, then the PASSWORD() function is evaluated by the specific authentication plugin used by the account. The authentication plugin hashes the password with a method that is compatible with that specific authentication plugin.

The unix_socket, named_pipe, gssapi, and pam authentication plugins do not store passwords in the mysql.global_priv table. These authentication plugins rely on other methods to authenticate the user.

If you attempt to run SET PASSWORD on an account that authenticates with one of these authentication plugins that doesn't store a password in the mysql.global_priv table, then MariaDB Server will raise a warning like the following:

SET PASSWORD is ignored for users authenticating via unix_socket plugin

See Authentication from MariaDB 10.4 for an overview of authentication changes in MariaDB 10.4.

MariaDB until 10.3

In MariaDB 10.3 and before, SET PASSWORD (with or without PASSWORD()) only works for accounts authenticated via mysql_native_password or mysql_old_password authentication plugins

Passwordless User Accounts

User accounts do not always require passwords to login.

The unix_socket , named_pipe and gssapi authentication plugins do not require a password to authenticate the user.

The pam authentication plugin may or may not require a password to authenticate the user, depending on the specific configuration.

The mysql_native_password and mysql_old_password authentication plugins require passwords for authentication, but the password can be blank. In that case, no password is required.

If you provide a password while attempting to log into the server as an account that doesn't require a password, then MariaDB server will simply ignore the password.

MariaDB starting with 10.4

In MariaDB 10.4 and later, a user account can be defined to use multiple authentication plugins in a specific order of preference. This specific scenario may be more noticeable in these versions, since an account could be associated with some authentication plugins that require a password, and some that do not.

Example

For example, if you had an entry with User and Host column values of 'bob' and '%.loc.gov', you would write the statement like this:

SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

If you want to delete a password for a user, you would do:

SET PASSWORD FOR 'bob'@localhost = PASSWORD("");

See Also

1.1.1.8 CREATE ROLE

Syntax

CREATE [OR REPLACE] ROLE [IF NOT EXISTS] role 
  [WITH ADMIN 
    {CURRENT_USER | CURRENT_ROLE | user | role}]

Description

The CREATE ROLE statement creates one or more MariaDB roles. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE ROLE creates a new row in the mysql.user table that has no privileges, and with the corresponding is_role field set to Y. It also creates a record in the mysql.roles_mapping table.

If any of the specified roles already exist, ERROR 1396 (HY000) results. If an error occurs, CREATE ROLE will still create the roles that do not result in an error. The maximum length for a role is 128 characters. Role names can be quoted, as explained in the Identifier names page. Only one error is produced for all roles which have not been created:

ERROR 1396 (HY000): Operation CREATE ROLE failed for 'a','b','c'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

PUBLIC and NONE are reserved, and cannot be used as role names. NONE is used to unset a role and PUBLIC has a special use in other systems, such as Oracle, so is reserved for compatibility purposes.

Before MariaDB 10.1.13, the CREATE ROLE statement was not permitted in prepared statements.

For valid identifiers to use as role names, see Identifier Names.

WITH ADMIN

The optional WITH ADMIN clause determines whether the current user, the current role or another user or role has use of the newly created role. If the clause is omitted, WITH ADMIN CURRENT_USER is treated as the default, which means that the current user will be able to GRANT this role to users.

OR REPLACE

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP ROLE IF EXISTS name;
CREATE ROLE name ...;

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified role already exists. Cannot be used together with the OR REPLACE clause.

Examples

CREATE ROLE journalist;

CREATE ROLE developer WITH ADMIN lorinda@localhost;

Granting the role to another user. Only user lorinda@localhost has permission to grant the developer role:

 SELECT USER();
+-------------------+
| USER()            |
+-------------------+
| henning@localhost |
+-------------------+
...
GRANT developer TO ian@localhost;
Access denied for user 'henning'@'localhost'

 SELECT USER();
+-------------------+
| USER()            |
+-------------------+
| lorinda@localhost |
+-------------------+

GRANT m_role TO ian@localhost;

The OR REPLACE and IF NOT EXISTS clauses. The journalist role already exists:

CREATE ROLE journalist;
ERROR 1396 (HY000): Operation CREATE ROLE failed for 'journalist'

CREATE OR REPLACE ROLE journalist;
Query OK, 0 rows affected (0.00 sec)

CREATE ROLE IF NOT EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+---------------------------------------------------+
| Level | Code | Message                                           |
+-------+------+---------------------------------------------------+
| Note  | 1975 | Can't create role 'journalist'; it already exists |
+-------+------+---------------------------------------------------+

See Also

1.1.1.9 DROP ROLE

Syntax

DROP ROLE [IF EXISTS] role_name [,role_name ...]

Description

The DROP ROLE statement removes one or more MariaDB roles. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database.

DROP ROLE does not disable roles for connections which selected them with SET ROLE. If a role has previously been set as a default role, DROP ROLE does not remove the record of the default role from the mysql.user table. If the role is subsequently recreated and granted, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this.

If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP ROLE will still drop the roles that do not result in an error. Only one error is produced for all roles which have not been dropped:

ERROR 1396 (HY000): Operation DROP ROLE failed for 'a','b','c'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

Before MariaDB 10.1.13, the DROP ROLE statement was not permitted in prepared statements.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a warning instead of an error if the role does not exist.

Examples

DROP ROLE journalist;

The same thing using the optional IF EXISTS clause:

DROP ROLE journalist;
ERROR 1396 (HY000): Operation DROP ROLE failed for 'journalist'

DROP ROLE IF EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)

Note (Code 1975): Can't drop role 'journalist'; it doesn't exist

See Also

1.1.1.10 SET ROLE

Syntax

SET ROLE { role | NONE }

Description

The SET ROLE statement enables a role, along with all of its associated permissions, for the current session. To unset a role, use NONE .

If a role that doesn't exist, or to which the user has not been assigned, is specified, an ERROR 1959 (OP000): Invalid role specification error occurs.

An automatic SET ROLE is implicitly performed when a user connects if that user has been assigned a default role. See SET DEFAULT ROLE.

Example

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE staff;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff        |
+--------------+

SET ROLE NONE;

SELECT CURRENT_ROLE();
+----------------+
| CURRENT_ROLE() |
+----------------+
| NULL           |
+----------------+

1.1.1.11 SET DEFAULT ROLE

Syntax

SET DEFAULT ROLE { role | NONE } [ FOR user@host ]

Description

The SET DEFAULT ROLE statement sets a default role for a specified (or current) user. A default role is automatically enabled when a user connects (an implicit SET ROLE statement is executed immediately after a connection is established).

To be able to set a role as a default, the role must already have been granted to that user, and one needs the privileges to enable this role (if you cannot do SET ROLE X, you won't be able to do SET DEFAULT ROLE X). To set a default role for another user one needs to have write access to the mysql database.

To remove a user's default role, use SET DEFAULT ROLE NONE [ FOR user@host ]. The record of the default role is not removed if the role is dropped or revoked, so if the role is subsequently re-created or granted, it will again be the user's default role.

The default role is stored in the default_role column in the mysql.user table/view, as well as in the Information Schema APPLICABLE_ROLES table, so these can be viewed to see which role has been assigned to a user as the default.

Examples

Setting a default role for the current user:

SET DEFAULT ROLE journalist;

Removing a default role from the current user:

SET DEFAULT ROLE NONE;

Setting a default role for another user. The role has to have been granted to the user before it can be set as default:

CREATE ROLE journalist;
CREATE USER taniel;

SET DEFAULT ROLE journalist FOR taniel;
ERROR 1959 (OP000): Invalid role specification `journalist`

GRANT journalist TO taniel;
SET DEFAULT ROLE journalist FOR taniel;

Viewing mysql.user:

select * from mysql.user where user='taniel'\G
*************************** 1. row ***************************
                  Host: %
                  User: taniel
...
               is_role: N
          default_role: journalist
...

Removing a default role for another user

SET DEFAULT ROLE NONE FOR taniel; 

1.1.1.12 SHOW GRANTS

Syntax

SHOW GRANTS [FOR user|role]

Description

The SHOW GRANTS statement lists privileges granted to a particular user or role.

Users

The statement lists the GRANT statement or statements that must be issued to duplicate the privileges that are granted to a MariaDB user account. The account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see GRANT.

SHOW GRANTS FOR 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+

To list the privileges granted to the account that you are using to connect to the server, you can use any of the following statements:

SHOW GRANTS;
SHOW GRANTS FOR CURRENT_USER;
SHOW GRANTS FOR CURRENT_USER();

If SHOW GRANTS FOR CURRENT_USER (or any of the equivalent syntaxes) is used in DEFINER context (such as within a stored procedure that is defined with SQL SECURITY DEFINER), the grants displayed are those of the definer and not the invoker.

Note that the DELETE HISTORY privilege, introduced in MariaDB 10.3.4, was displayed as DELETE VERSIONING ROWS when running SHOW GRANTS until MariaDB 10.3.15 (MDEV-17655).

Roles

SHOW GRANTS can also be used to view the privileges granted to a role.

Example

SHOW GRANTS FOR journalist;
+------------------------------------------+
| Grants for journalist                    |
+------------------------------------------+
| GRANT USAGE ON *.* TO 'journalist'       |
| GRANT DELETE ON `test`.* TO 'journalist' |
+------------------------------------------+

See Also

1.1.1.13 SHOW CREATE USER

MariaDB starting with 10.2.0

SHOW CREATE USER was introduced in MariaDB 10.2.0

Syntax

SHOW CREATE USER user_name

Description

Shows the CREATE USER statement that created the given user. The statement requires the SELECT privilege for the mysql database, except for the current user.

Examples

CREATE USER foo4@test require cipher 'text' 
  issuer 'foo_issuer' subject 'foo_subject';

SHOW CREATE USER foo4@test\G
*************************** 1. row ***************************
CREATE USER 'foo4'@'test' 
  REQUIRE ISSUER 'foo_issuer' 
  SUBJECT 'foo_subject' 
  CIPHER 'text'

User Password Expiry:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;

SHOW CREATE USER 'monty'@'localhost';
+------------------------------------------------------------------+
| CREATE USER for monty@localhost                                  |
+------------------------------------------------------------------+
| CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY |
+------------------------------------------------------------------+

See Also

1.1.2. Administrative SQL Statements

1.1.2.1 Table Statements

1.1.2.1.1 ALTER

1.1.2.1.1.1 ALTER TABLE

Syntax

ALTER [ONLINE] [IGNORE] TABLE [IF EXISTS] tbl_name [WAIT n | NOWAIT] alter_specification [, alter_specification] ...

alter_specification: table_option ... | ADD [COLUMN] [IF NOT EXISTS] col_name column_definition [FIRST | AFTER col_name ] | ADD [COLUMN] [IF NOT EXISTS] (col_name column_definition,...) | ADD {INDEX|KEY} [IF NOT EXISTS] [index_name] [index_type] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name,...) [index_option] ... | ADD FULLTEXT [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | ADD SPATIAL [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | ADD [CONSTRAINT [symbol]] FOREIGN KEY [IF NOT EXISTS] [index_name] (index_col_name,...) reference_definition | ADD PERIOD FOR SYSTEM_TIME (start_column_name, end_column_name) | ALTER [COLUMN] col_name SET DEFAULT literal | (expression) | ALTER [COLUMN] col_name DROP DEFAULT | ALTER {INDEX|KEY} index_name [NOT] INVISIBLE | CHANGE [COLUMN] [IF EXISTS] old_col_name new_col_name column_definition [FIRST|AFTER col_name] | MODIFY [COLUMN] [IF EXISTS] col_name column_definition [FIRST | AFTER col_name] | DROP [COLUMN] [IF EXISTS] col_name [RESTRICT|CASCADE] | DROP PRIMARY KEY | DROP {INDEX|KEY} [IF EXISTS] index_name | DROP FOREIGN KEY [IF EXISTS] fk_symbol | DROP CONSTRAINT [IF EXISTS] constraint_name | DISABLE KEYS | ENABLE KEYS | RENAME [TO] new_tbl_name | ORDER BY col_name [, col_name] ... | RENAME COLUMN old_col_name TO new_col_name | RENAME {INDEX|KEY} old_index_name TO new_index_name | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name] | [DEFAULT] CHARACTER SET [=] charset_name | [DEFAULT] COLLATE [=] collation_name | DISCARD TABLESPACE | IMPORT TABLESPACE | ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT} | LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE} | FORCE | partition_options | ADD PARTITION [IF NOT EXISTS] (partition_definition) | DROP PARTITION [IF EXISTS] partition_names | COALESCE PARTITION number | REORGANIZE PARTITION [partition_names INTO (partition_definitions)] | ANALYZE PARTITION partition_names | CHECK PARTITION partition_names | OPTIMIZE PARTITION partition_names | REBUILD PARTITION partition_names | REPAIR PARTITION partition_names | EXCHANGE PARTITION partition_name WITH TABLE tbl_name | REMOVE PARTITIONING | ADD SYSTEM VERSIONING | DROP SYSTEM VERSIONING

index_col_name: col_name [(length)] [ASC | DESC]

index_type: USING {BTREE | HASH | RTREE}

index_option: [ KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' | CLUSTERING={YES| NO} ] [ IGNORED | NOT IGNORED ]

table_options: table_option [[,] table_option] ...

Description

ALTER TABLE enables you to change the structure of an existing table. For example, you can add or delete columns, create or destroy indexes, change the type of existing columns, or rename columns or the table itself. You can also change the comment for the table and the storage engine of the table.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

When adding a UNIQUE index on a column (or a set of columns) which have duplicated values, an error will be produced and the statement will be stopped. To suppress the error and force the creation of UNIQUE indexes, discarding duplicates, the IGNORE option can be specified. This can be useful if a column (or a set of columns) should be UNIQUE but it contains duplicate values; however, this technique provides no control on which rows are preserved and which are deleted. Also, note that IGNORE is accepted but ignored in ALTER TABLE ... EXCHANGE PARTITION statements.

This statement can also be used to rename a table. For details see RENAME TABLE.

When an index is created, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for REPAIR TABLE. InnoDB allocates three buffers whose size is defined by innodb_sort_buffer_size.

Privileges

Executing the ALTER TABLE statement generally requires at least the ALTER privilege for the table or the database..

If you are renaming a table, then it also requires the DROP, CREATE and INSERT privileges for the table or the database as well.

Online DDL

Online DDL is supported with the ALGORITHM and LOCK clauses.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

ALTER ONLINE TABLE

ALTER ONLINE TABLE also works for partitioned tables.

Online ALTER TABLE is available by executing the following:

ALTER ONLINE TABLE ...;

This statement has the following semantics:

This statement is equivalent to the following:

ALTER TABLE ... LOCK=NONE;

See the LOCK alter specification for more information. <</product>>

This statement is equivalent to the following:

ALTER TABLE ... ALGORITHM=INPLACE;

See the ALGORITHM alter specification for more information. <</product>>

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

IF EXISTS

The IF EXISTS and IF NOT EXISTS clauses are available for the following:

ADD COLUMN [IF NOT EXISTS] ADD INDEX [IF NOT EXISTS] ADD FOREIGN KEY [IF NOT EXISTS] ADD PARTITION [IF NOT EXISTS] CREATE INDEX [IF NOT EXISTS]

DROP COLUMN [IF EXISTS] DROP INDEX [IF EXISTS] DROP FOREIGN KEY [IF EXISTS] DROP PARTITION [IF EXISTS] CHANGE COLUMN [IF EXISTS] MODIFY COLUMN [IF EXISTS] DROP INDEX [IF EXISTS]

When IF EXISTS and IF NOT EXISTS are used in clauses, queries will not report errors when the condition is triggered for that clause. A warning with the same message text will be issued and the ALTER will move on to the next clause in the statement (or end if finished). <</product>>

MariaDB starting with 10.5.2

If this is directive is used after ALTER ... TABLE, one will not get an error if the table doesn't exist.

Column Definitions

See CREATE TABLE: Column Definitions for information about column definitions.

Index Definitions

See CREATE TABLE: Index Definitions for information about index definitions.

The CREATE INDEX and DROP INDEX statements can also be used to add or remove an index.

Character Sets and Collations

CONVERT TO CHARACTER SET charset_name [COLLATE collation_name] [DEFAULT] CHARACTER SET [=] charset_name [DEFAULT] COLLATE [=] collation_name

See Setting Character Sets and Collations for details on setting the character sets and collations.

Alter Specifications

Table Options

See CREATE TABLE: Table Options for information about table options.

ADD COLUMN

... ADD COLUMN [IF NOT EXISTS] (col_name column_definition,...)

Adds a column to the table. The syntax is the same as in CREATE TABLE. If you are using IF NOT_EXISTS the column will not be added if it was not there already. This is very useful when doing scripts to modify tables.

The FIRST and AFTER clauses affect the physical order of columns in the datafile. Use FIRST to add a column in the first (leftmost) position, or AFTER followed by a column name to add the new column in any other position. Note that, nowadays, the physical position of a column is usually irrelevant.

See also Instant ADD COLUMN for InnoDB.

DROP COLUMN

... DROP COLUMN [IF EXISTS] col_name [CASCADE|RESTRICT]

Drops the column from the table. If you are using IF EXISTS you will not get an error if the column didn't exist. If the column is part of any index, the column will be dropped from them, except if you add a new column with identical name at the same time. The index will be dropped if all columns from the index were dropped. If the column was used in a view or trigger, you will get an error next time the view or trigger is accessed.

MariaDB starting with 10.2.8

Dropping a column that is part of a multi-column UNIQUE constraint is not permitted. For example:

CREATE TABLE a (
  a int,
  b int,
  primary key (a,b)
);

ALTER TABLE x DROP COLUMN a;
[42000][1072] Key column 'A' doesn't exist in table

The reason is that dropping column a would result in the new constraint that all values in column b be unique. In order to drop the column, an explicit DROP PRIMARY KEY and ADD PRIMARY KEY would be required. Up until MariaDB 10.2.7, the column was dropped and the additional constraint applied, resulting in the following structure:

ALTER TABLE x DROP COLUMN a;
Query OK, 0 rows affected (0.46 sec)

DESC x;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| b     | int(11) | NO   | PRI | NULL    |       |
+-------+---------+------+-----+---------+-------+
MariaDB starting with 10.4.0

MariaDB 10.4.0 supports instant DROP COLUMN. DROP COLUMN of an indexed column would imply DROP INDEX (and in the case of a non-UNIQUE multi-column index, possibly ADD INDEX). These will not be allowed with ALGORITHM=INSTANT, but unlike before, they can be allowed with ALGORITHM=NOCOPY

RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing.

MODIFY COLUMN

Allows you to modify the type of a column. The column will be at the same place as the original column and all indexes on the column will be kept. Note that when modifying column, you should specify all attributes for the new column.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY((a));
ALTER TABLE t1 MODIFY a BIGINT UNSIGNED AUTO_INCREMENT;

CHANGE COLUMN

Works like MODIFY COLUMN except that you can also change the name of the column. The column will be at the same place as the original column and all index on the column will be kept.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY(a));
ALTER TABLE t1 CHANGE a b BIGINT UNSIGNED AUTO_INCREMENT;

ALTER COLUMN

This lets you change column options.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, b varchar(50), PRIMARY KEY(a));
ALTER TABLE t1 ALTER b SET DEFAULT 'hello';

RENAME INDEX/KEY

MariaDB starting with 10.5.2

From MariaDB 10.5.2, it is possible to rename an index using the RENAME INDEX (or RENAME KEY) syntax, for example:

ALTER TABLE t1 RENAME INDEX i_old TO i_new;

RENAME COLUMN

MariaDB starting with 10.5.2

From MariaDB 10.5.2, it is possible to rename a column using the RENAME COLUMN syntax, for example:

ALTER TABLE t1 RENAME COLUMN c_old TO c_new;

ADD PRIMARY KEY

Add a primary key.

For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY.

See Getting Started with Indexes: Primary Key for more information.

DROP PRIMARY KEY

Drop a primary key.

For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY.

See Getting Started with Indexes: Primary Key for more information.

ADD FOREIGN KEY

Add a foreign key.

For FOREIGN KEY indexes, a reference definition must be provided.

For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

First, you have to specify the name of the target (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed:

  • RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300').
  • NO ACTION: Synonym for RESTRICT.
  • CASCADE: The delete/update operation is performed in both tables.
  • SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed).
  • SET DEFAULT: This option is implemented only for the legacy PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted.

If either clause is omitted, the default behavior for the omitted clause is RESTRICT.

See Foreign Keys for more information.

DROP FOREIGN KEY

Drop a foreign key.

See Foreign Keys for more information.

ADD INDEX

Add a plain index.

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

DROP INDEX

Drop a plain index.

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

ADD UNIQUE INDEX

Add a unique index.

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

DROP UNIQUE INDEX

Drop a unique index.

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

ADD FULLTEXT INDEX

Add a FULLTEXT index.

See Full-Text Indexes for more information.

DROP FULLTEXT INDEX

Drop a FULLTEXT index.

See Full-Text Indexes for more information.

ADD SPATIAL INDEX

Add a SPATIAL index.

See SPATIAL INDEX for more information.

DROP SPATIAL INDEX

Drop a SPATIAL index.

See SPATIAL INDEX for more information.

ENABLE/ DISABLE KEYS

DISABLE KEYS will disable all non unique keys for the table for storage engines that support this (at least MyISAM and Aria). This can be used to speed up inserts into empty tables.

ENABLE KEYS will enable all disabled keys.

RENAME TO

Renames the table. See also RENAME TABLE.

ADD CONSTRAINT

Modifies the table adding a constraint on a particular column or columns.

MariaDB starting with 10.2.1

MariaDB 10.2.1 introduced new ways to define a constraint.

Note: Before MariaDB 10.2.1, constraint expressions were accepted in syntax, but ignored.

ALTER TABLE table_name ADD CONSTRAINT [constraint_name] CHECK(expression);

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint fails, then the row will not be updated. One can use most deterministic functions in a constraint, including UDF's.

CREATE TABLE account_ledger (
	id INT PRIMARY KEY AUTO_INCREMENT,
	transaction_name VARCHAR(100),
	credit_account VARCHAR(100),
	credit_amount INT,
	debit_account VARCHAR(100),
	debit_amount INT);

ALTER TABLE account_ledger 
ADD CONSTRAINT is_balanced 
    CHECK((debit_amount + credit_amount) = 0);

The constraint_name is optional. If you don't provide one in the ALTER TABLE statement, MariaDB auto-generates a name for you. This is done so that you can remove it later using DROP CONSTRAINT clause.

You can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. You may find this useful when loading a table that violates some constraints that you want to later find and fix in SQL.

To view constraints on a table, query information_schema.TABLE_CONSTRAINTS:

SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE 
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 'account_ledger';

+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME     | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| is_balanced     | account_ledger | CHECK           |
+-----------------+----------------+-----------------+

DROP CONSTRAINT

MariaDB starting with 10.2.22

DROP CONSTRAINT for UNIQUE and FOREIGN KEY constraints was introduced in MariaDB 10.2.22 and MariaDB 10.3.13.

MariaDB starting with 10.2.1

DROP CONSTRAINT for CHECK constraints was introduced in MariaDB 10.2.1

Modifies the table, removing the given constraint.

ALTER TABLE table_name
DROP CONSTRAINT constraint_name;

When you add a constraint to a table, whether through a CREATE TABLE or ALTER TABLE...ADD CONSTRAINT statement, you can either set a constraint_name yourself, or allow MariaDB to auto-generate one for you. To view constraints on a table, query information_schema.TABLE_CONSTRAINTS. For instance,

CREATE TABLE t (
   a INT,
   b INT,
   c INT,
   CONSTRAINT CHECK(a > b),
   CONSTRAINT check_equals CHECK(a = c)); 

SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE 
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 't';

+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME     | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| check_equals    | t              | CHECK           |
| CONSTRAINT_1    | t              | CHECK           |
+-----------------+----------------+-----------------+

To remove a constraint from the table, issue an ALTER TABLE...DROP CONSTRAINT statement. For example,

ALTER TABLE t DROP CONSTRAINT is_unique;

ADD SYSTEM VERSIONING

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

Add system versioning.

DROP SYSTEM VERSIONING

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

Drop system versioning.

ADD PERIOD FOR SYSTEM_TIME

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

FORCE

ALTER TABLE ... FORCE can force MariaDB to re-build the table.

In MariaDB 5.5 and before, this could only be done by setting the ENGINE table option to its old value. For example, for an InnoDB table, one could execute the following:

ALTER TABLE tab_name ENGINE = InnoDB;

The FORCE option can be used instead. For example, :

ALTER TABLE tab_name FORCE;

With InnoDB, the table rebuild will only reclaim unused space (i.e. the space previously used for deleted rows) if the innodb_file_per_table system variable is set to ON. If the system variable is OFF, then the space will not be reclaimed, but it will be-re-used for new data that's later added.

EXCHANGE PARTITION

This is used to exchange the tablespace files between a partition and another table.

See copying InnoDB's transportable tablespaces for more information.

DISCARD TABLESPACE

This is used to discard an InnoDB table's tablespace.

See copying InnoDB's transportable tablespaces for more information.

IMPORT TABLESPACE

This is used to import an InnoDB table's tablespace. The tablespace should have been copied from its original server after executing FLUSH TABLES FOR EXPORT.

See copying InnoDB's transportable tablespaces for more information.

ALTER TABLE ... IMPORT only applies to InnoDB tables. Most other popular storage engines, such as Aria and MyISAM, will recognize their data files as soon as they've been placed in the proper directory under the datadir, and no special DDL is required to import them.

ALGORITHM

The ALTER TABLE statement supports the ALGORITHM clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different algorithms. An algorithm can be explicitly chosen for an ALTER TABLE operation by setting the ALGORITHM clause. The supported values are:

  • ALGORITHM=DEFAULT - This implies the default behavior for the specific statement, such as if no ALGORITHM clause is specified.
  • ALGORITHM=COPY
  • ALGORITHM=INPLACE
  • ALGORITHM=NOCOPY - This was added in MariaDB 10.3.7.
  • ALGORITHM=INSTANT - This was added in MariaDB 10.3.7.

See InnoDB Online DDL Overview: ALGORITHM for information on how the ALGORITHM clause affects InnoDB.

ALGORITHM=DEFAULT

The default behavior, which occurs if ALGORITHM=DEFAULT is specified, or if ALGORITHM is not specified at all, usually only makes a copy if the operation doesn't support being done in-place at all. In this case, the most efficient available algorithm will usually be used.

However, in MariaDB 10.3.6 and before, if the value of the old_alter_table system variable is set to ON, then the default behavior is to perform ALTER TABLE operations by making a copy of the table using the old algorithm.

In MariaDB 10.3.7 and later, the old_alter_table system variable is deprecated. Instead, the alter_algorithm system variable defines the default algorithm for ALTER TABLE operations.

ALGORITHM=COPY

ALGORITHM=COPY is the name for the original ALTER TABLE algorithm from early MariaDB versions.

When ALGORITHM=COPY is set, MariaDB essentially does the following operations:

-- Create a temporary table with the new definition
CREATE TEMPORARY TABLE tmp_tab (
...
);

-- Copy the data from the original table
INSERT INTO tmp_tab
   SELECT * FROM original_tab;

-- Drop the original table
DROP TABLE original_tab;

-- Rename the temporary table, so that it replaces the original one
RENAME TABLE tmp_tab TO original_tab;

This algorithm is very inefficient, but it is generic, so it works for all storage engines.

If ALGORITHM=COPY is specified, then the copy algorithm will be used even if it is not necessary. This can result in a lengthy table copy. If multiple ALTER TABLE operations are required that each require the table to be rebuilt, then it is best to specify all operations in a single ALTER TABLE statement, so that the table is only rebuilt once.

ALGORITHM=INPLACE

ALGORITHM=COPY can be incredibly slow, because the whole table has to be copied and rebuilt. ALGORITHM=INPLACE was introduced as a way to avoid this by performing operations in-place and avoiding the table copy and rebuild, when possible.

When ALGORITHM=INPLACE is set, the underlying storage engine uses optimizations to perform the operation while avoiding the table copy and rebuild. However, INPLACE is a bit of a misnomer, since some operations may still require the table to be rebuilt for some storage engines. Regardless, several operations can be performed without a full copy of the table for some storage engines.

A more accurate name would have been ALGORITHM=ENGINE, where ENGINE refers to an "engine-specific" algorithm.

If an ALTER TABLE operation supports ALGORITHM=INPLACE, then it can be performed using optimizations by the underlying storage engine, but it may rebuilt.

See InnoDB Online DDL Operations with ALGORITHM=INPLACE for more.

ALGORITHM=NOCOPY

ALGORITHM=NOCOPY was introduced in MariaDB 10.3.7.

ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to rebuild the clustered index, because when the clustered index has to be rebuilt, the whole table has to be rebuilt. ALGORITHM=NOCOPY was introduced as a way to avoid this.

If an ALTER TABLE operation supports ALGORITHM=NOCOPY, then it can be performed without rebuilding the clustered index.

If ALGORITHM=NOCOPY is specified for an ALTER TABLE operation that does not support ALGORITHM=NOCOPY, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to rebuild the clustered index, and perform unexpectedly slowly.

See InnoDB Online DDL Operations with ALGORITHM=NOCOPY for more.

ALGORITHM=INSTANT

ALGORITHM=INSTANT was introduced in MariaDB 10.3.7.

ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to modify data files. ALGORITHM=INSTANT was introduced as a way to avoid this.

If an ALTER TABLE operation supports ALGORITHM=INSTANT, then it can be performed without modifying any data files.

If ALGORITHM=INSTANT is specified for an ALTER TABLE operation that does not support ALGORITHM=INSTANT, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to modify data files, and perform unexpectedly slowly.

See InnoDB Online DDL Operations with ALGORITHM=INSTANT for more.

LOCK

The ALTER TABLE statement supports the LOCK clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different locking strategies. A locking strategy can be explicitly chosen for an ALTER TABLE operation by setting the LOCK clause. The supported values are:

  • DEFAULT: Acquire the least restrictive lock on the table that is supported for the specific operation. Permit the maximum amount of concurrency that is supported for the specific operation.
  • NONE: Acquire no lock on the table. Permit all concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised.
  • SHARED: Acquire a read lock on the table. Permit read-only concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised.
  • EXCLUSIVE: Acquire a write lock on the table. Do not permit concurrent DML.

Different storage engines support different locking strategies for different operations. If a specific locking strategy is chosen for an ALTER TABLE operation, and that table's storage engine does not support that locking strategy for that specific operation, then an error will be raised.

If the LOCK clause is not explicitly set, then the operation uses LOCK=DEFAULT.

ALTER ONLINE TABLE is equivalent to LOCK=NONE. Therefore, the ALTER ONLINE TABLE statement can be used to ensure that your ALTER TABLE operation allows all concurrent DML.

See InnoDB Online DDL Overview: LOCK for information on how the LOCK clause affects InnoDB.

Progress Reporting

MariaDB provides progress reporting for ALTER TABLE statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

ALTER TABLE test ENGINE=Aria;
Stage: 1 of 2 'copy to tmp table'    46% of stage

The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table.

See Progress Reporting for more information.

Aborting ALTER TABLE Operations

If an ALTER TABLE operation is being performed and the connection is killed, the changes will be rolled back in a controlled manner. The rollback can be a slow operation as the time it takes is relative to how far the operation has progressed.

MariaDB starting with 10.2.13

Aborting ALTER TABLE ... ALGORITHM=COPY was made faster by removing excessive undo logging (MDEV-11415). This significantly shortens the time it takes to abort a running ALTER TABLE operation.

Atomic ALTER TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, ALTER TABLE is atomic for most engines, including InnoDB, MyRocks, MyISAM and Aria (MDEV-25180). This means that if there is a crash (server down or power outage) during an ALTER TABLE operation, after recovery, either the old table and associated triggers and status will be intact, or the new table will be active.

In older MariaDB versions one could get leftover #sql-alter..', '#sql-backup..' or 'table_name.frm˝' files if the system crashed during the ALTER TABLE operation.

See Atomic DDL for more information.

Replication

MariaDB starting with 10.8.0

Before MariaDB 10.8.0, ALTER TABLE got fully executed on the primary first, and only then was it replicated and started executing on replicas. From MariaDB 10.8.0, ALTER TABLE gets replicated and starts executing on replicas when it starts executing on the primary, not when it finishes. This way the replication lag caused by a heavy ALTER TABLE can be completely eliminated (MDEV-11675).

Examples

Adding a new column:

ALTER TABLE t1 ADD x INT;

Dropping a column:

ALTER TABLE t1 DROP x;

Modifying the type of a column:

ALTER TABLE t1 MODIFY x bigint unsigned;

Changing the name and type of a column:

ALTER TABLE t1 CHANGE a b bigint unsigned auto_increment;

Combining multiple clauses in a single ALTER TABLE statement, separated by commas:

ALTER TABLE t1 DROP x, ADD x2 INT,  CHANGE y y2 INT;

Changing the storage engine and adding a comment:

ALTER TABLE t1 
  ENGINE = InnoDB 
  COMMENT = 'First of three tables containing usage info';

Rebuilding the table (the previous example will also rebuild the table if it was already InnoDB):

ALTER TABLE t1 FORCE;

Dropping an index:

ALTER TABLE rooms DROP INDEX u;

Adding a unique index:

ALTER TABLE rooms ADD UNIQUE INDEX u(room_number);

From MariaDB 10.5.3, adding a primary key for an application-time period table with a WITHOUT OVERLAPS constraint:

ALTER TABLE rooms ADD PRIMARY KEY(room_number, p WITHOUT OVERLAPS);

See Also

1.1.2.1.1.2 ALTER DATABASE

Modifies a database, changing its overall characteristics.

Syntax

ALTER {DATABASE | SCHEMA} [db_name]
    alter_specification ...
ALTER {DATABASE | SCHEMA} db_name
    UPGRADE DATA DIRECTORY NAME

alter_specification:
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'comment'

Description

ALTER DATABASE enables you to change the overall characteristics of a database. These characteristics are stored in the db.opt file in the database directory. To use ALTER DATABASE, you need the ALTER privilege on the database. ALTER SCHEMA is a synonym for ALTER DATABASE.

The CHARACTER SET clause changes the default database character set. The COLLATE clause changes the default database collation. See Character Sets and Collations for more.

You can see what character sets and collations are available using, respectively, the SHOW CHARACTER SET and SHOW COLLATION statements.

Changing the default character set/collation of a database does not change the character set/collation of any stored procedures or stored functions that were previously created, and relied on the defaults. These need to be dropped and recreated in order to apply the character set/collation changes.

The database name can be omitted from the first syntax, in which case the statement applies to the default database.

The syntax that includes the UPGRADE DATA DIRECTORY NAME clause was added in MySQL 5.1.23. It updates the name of the directory associated with the database to use the encoding implemented in MySQL 5.1 for mapping database names to database directory names (see Identifier to File Name Mapping). This clause is for use under these conditions:

  • It is intended when upgrading MySQL to 5.1 or later from older versions.
  • It is intended to update a database directory name to the current encoding format if the name contains special characters that need encoding.
  • The statement is used by mysqlcheck (as invoked by mysql_upgrade).

For example,if a database in MySQL 5.0 has a name of a-b-c, the name contains instance of the `-' character. In 5.0, the database directory is also named a-b-c, which is not necessarily safe for all file systems. In MySQL 5.1 and up, the same database name is encoded as a@002db@002dc to produce a file system-neutral directory name.

When a MySQL installation is upgraded to MySQL 5.1 or later from an older version,the server displays a name such as a-b-c (which is in the old format) as #mysql50#a-b-c, and you must refer to the name using the #mysql50# prefix. Use UPGRADE DATA DIRECTORY NAME in this case to explicitly tell the server to re-encode the database directory name to the current encoding format:

ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME;

After executing this statement, you can refer to the database as a-b-c without the special #mysql50# prefix.

COMMENT

MariaDB starting with 10.5.0

From MariaDB 10.5.0, it is possible to add a comment of a maximum of 1024 bytes. If the comment length exceeds this length, a error/warning code 4144 is thrown. The database comment is also added to the db.opt file, as well as to the information_schema.schemata table.

Examples

ALTER DATABASE test CHARACTER SET='utf8'  COLLATE='utf8_bin';

From MariaDB 10.5.0:

ALTER DATABASE p COMMENT='Presentations';

See Also

1.1.2.1.1.3 ALTER EVENT

Modifies one or more characteristics of an existing event.

Syntax

ALTER
    [DEFINER = { user | CURRENT_USER }]
    EVENT event_name
    [ON SCHEDULE schedule]
    [ON COMPLETION [NOT] PRESERVE]
    [RENAME TO new_event_name]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    [DO sql_statement]

Description

The ALTER EVENT statement is used to change one or more of the characteristics of an existing event without the need to drop and recreate it. The syntax for each of the DEFINER, ON SCHEDULE, ON COMPLETION, COMMENT, ENABLE / DISABLE, and DO clauses is exactly the same as when used with CREATE EVENT.

This statement requires the EVENT privilege. When a user executes a successful ALTER EVENT statement, that user becomes the definer for the affected event.

(In MySQL 5.1.11 and earlier, an event could be altered only by its definer, or by a user having the SUPER privilege.)

ALTER EVENT works only with an existing event:

ALTER EVENT no_such_event ON SCHEDULE EVERY '2:3' DAY_HOUR;
ERROR 1539 (HY000): Unknown event 'no_such_event'

Examples

ALTER EVENT myevent 
  ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 2 HOUR 
  DO 
    UPDATE myschema.mytable SET mycol = mycol + 1;

See Also

1.1.2.1.1.4 ALTER FUNCTION

Syntax

ALTER FUNCTION func_name [characteristic ...]

characteristic:
    { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

Description

This statement can be used to change the characteristics of a stored function. More than one change may be specified in an ALTER FUNCTION statement. However, you cannot change the parameters or body of a stored function using this statement; to make such changes, you must drop and re-create the function using DROP FUNCTION and CREATE FUNCTION.

You must have the ALTER ROUTINE privilege for the function. (That privilege is granted automatically to the function creator.) If binary logging is enabled, the ALTER FUNCTION statement might also require the SUPER privilege, as described in Binary Logging of Stored Routines.

Example

ALTER FUNCTION hello SQL SECURITY INVOKER;

See Also

1.1.2.1.1.5 ALTER LOGFILE GROUP

Syntax

ALTER LOGFILE GROUP logfile_group
    ADD UNDOFILE 'file_name'
    [INITIAL_SIZE [=] size]
    [WAIT]
    ENGINE [=] engine_name

The ALTER LOGFILE GROUP statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. See MDEV-19295 for more information.

1.1.2.1.1.6 ALTER PROCEDURE

Syntax

ALTER PROCEDURE proc_name [characteristic ...]

characteristic:
    { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

Description

This statement can be used to change the characteristics of a stored procedure. More than one change may be specified in an ALTER PROCEDURE statement. However, you cannot change the parameters or body of a stored procedure using this statement. To make such changes, you must drop and re-create the procedure using either CREATE OR REPLACE PROCEDURE (since MariaDB 10.1.3) or DROP PROCEDURE and CREATE PROCEDURE (MariaDB 10.1.2 and before).

You must have the ALTER ROUTINE privilege for the procedure. By default, that privilege is granted automatically to the procedure creator. See Stored Routine Privileges.

Example

ALTER PROCEDURE simpleproc SQL SECURITY INVOKER;

See Also

1.1.2.1.1.7 ALTER SEQUENCE

MariaDB starting with 10.3.1

ALTER SEQUENCE was introduced in MariaDB 10.3.

Syntax

ALTER SEQUENCE [IF EXISTS] sequence_name [ INCREMENT [ BY | = ] increment ] [ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ] [ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ] [ START [ WITH | = ] start ] [ CACHE [=] cache ] [ [ NO ] CYCLE ] [ RESTART [[WITH | =] restart]

ALTER SEQUENCE allows one to change any values for a SEQUENCE created with CREATE SEQUENCE.

The options for ALTER SEQUENCE can be given in any order.

Description

ALTER SEQUENCE changes the parameters of an existing sequence generator. Any parameters not specifically set in the ALTER SEQUENCE command retain their prior settings.

ALTER SEQUENCE requires the ALTER privilege.

Arguments to ALTER SEQUENCE

The following options may be used:

OptionDefault valueDescription
INCREMENT1Increment to use for values. May be negative.
MINVALUE1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0Minimum value for the sequence.
MAXVALUE9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0Max value for sequence.
STARTMINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0First value that the sequence will generate.
CACHE1000Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out.
CYCLE0 (= NO CYCLE)1 if the sequence should start again from MINVALUE# after it has run out of values.
RESTARTSTART if restart value not is given If RESTART option is used, NEXT VALUE will return the restart value.

The optional clause RESTART [ WITH restart ] sets the next value for the sequence. This is equivalent to calling the SETVAL() function with the is_used argument as 0. The specified value will be returned by the next call of nextval. Using RESTART with no restart value is equivalent to supplying the start value that was recorded by CREATE SEQUENCE or last set by ALTER SEQUENCE START WITH.

ALTER SEQUENCE will not allow you to change the sequence so that it's inconsistent. For example:

CREATE SEQUENCE s1;
ALTER SEQUENCE s1 MINVALUE 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting

ALTER SEQUENCE s1 MINVALUE 10 RESTART 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting

ALTER SEQUENCE s1 MINVALUE 10 START 10 RESTART 10;

INSERT

To allow SEQUENCE objects to be backed up by old tools, like mysqldump, one can use SELECT to read the current state of a SEQUENCE object and use an INSERT to update the SEQUENCE object. INSERT is only allowed if all fields are specified:

CREATE SEQUENCE s1;
INSERT INTO s1 VALUES(1000,10,2000,1005,1,1000,0,0);
SELECT * FROM s1;

+------------+-----------+-----------+-------+-----------+-------+-------+-------+
| next_value | min_value | max_value | start | increment | cache | cycle | round |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+
|       1000 |        10 |      2000 |  1005 |         1 |  1000 |     0 |     0 |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+

SHOW CREATE SEQUENCE s1;
+-------+--------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                 |
+-------+--------------------------------------------------------------------------------------------------------------+
| s1    | CREATE SEQUENCE `s1` start with 1005 minvalue 10 maxvalue 2000 increment by 1 cache 1000 nocycle ENGINE=Aria |
+-------+--------------------------------------------------------------------------------------------------------------+

Notes

ALTER SEQUENCE will instantly affect all future SEQUENCE operations. This is in contrast to some other databases where the changes requested by ALTER SEQUENCE will not be seen until the sequence cache has run out.

ALTER SEQUENCE will take a full table lock of the sequence object during its (brief) operation. This ensures that ALTER SEQUENCE is replicated correctly. If you only want to set the next sequence value to a higher value than current, then you should use SETVAL() instead, as this is not blocking.

If you want to change storage engine, sequence comment or rename the sequence, you can use ALTER TABLE for this.

See Also

1.1.2.1.1.8 ALTER SERVER

Syntax

ALTER SERVER server_name
    OPTIONS (option [, option] ...)

Description

Alters the server information for server_name, adjusting the specified options as per the CREATE SERVER command. The corresponding fields in the mysql.servers table are updated accordingly. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

ALTER SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

Examples

ALTER SERVER s OPTIONS (USER 'sally');

See Also

1.1.2.1.1.9 ALTER TABLESPACE

The ALTER TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

1.1.2.1.1.10

1.1.2.1.2 ALTER VIEW

Syntax

ALTER
    [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
    [DEFINER = { user | CURRENT_USER }]
    [SQL SECURITY { DEFINER | INVOKER }]
    VIEW view_name [(column_list)]
    AS select_statement
    [WITH [CASCADED | LOCAL] CHECK OPTION]

Description

This statement changes the definition of a view, which must exist. The syntax is similar to that for CREATE VIEW and the effect is the same as for CREATE OR REPLACE VIEW if the view exists. This statement requires the CREATE VIEW and DROP privileges for the view, and some privilege for each column referred to in the SELECT statement. ALTER VIEW is allowed only to the definer or users with the SUPER privilege.

Example

ALTER VIEW v AS SELECT a, a*3 AS a2 FROM t;

See Also

1.1.2.1.3 ANALYZE TABLE

Syntax

ANALYZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [,tbl_name ...] 
  [PERSISTENT FOR [ALL|COLUMNS ([col_name [,col_name ...]])] 
    [INDEXES ([index_name [,index_name ...]])]]           

Description

ANALYZE TABLE analyzes and stores the key distribution for a table (index statistics). This statement works with MyISAM, Aria and InnoDB tables. During the analysis, InnoDB will allow reads/writes, and MyISAM/Aria reads/inserts. For MyISAM tables, this statement is equivalent to using myisamchk --analyze.

For more information on how the analysis works within InnoDB, see InnoDB Limitations.

MariaDB uses the stored key distribution to decide the order in which tables should be joined when you perform a join on something other than a constant. In addition, key distributions can be used when deciding which indexes to use for a specific table within a query.

This statement requires SELECT and INSERT privileges for the table.

By default, ANALYZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, ANALYZE TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

ANALYZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... ANALYZE PARTITION to analyze one or more partitions.

The Aria storage engine supports progress reporting for the ANALYZE TABLE statement.

Engine-Independent Statistics

ANALYZE TABLE supports engine-independent statistics. See Engine-Independent Table Statistics: Collecting Statistics with the ANALYZE TABLE Statement for more information.

See Also

1.1.2.1.4 CHECK TABLE

Syntax

CHECK TABLE tbl_name [, tbl_name] ... [option] ...

option = {FOR UPGRADE | QUICK | FAST | MEDIUM | EXTENDED | CHANGED}

Description

CHECK TABLE checks a table or tables for errors. CHECK TABLE works for Archive, Aria, CSV, InnoDB, and MyISAM tables. For Aria and MyISAM tables, the key statistics are updated as well. For CSV, see also Checking and Repairing CSV Tables.

As an alternative, myisamchk is a commandline tool for checking MyISAM tables when the tables are not being accessed.

For checking dynamic columns integrity, COLUMN_CHECK() can be used.

CHECK TABLE can also check views for problems, such as tables that are referenced in the view definition that no longer exist.

CHECK TABLE is also supported for partitioned tables. You can use ALTER TABLE ... CHECK PARTITION to check one or more partitions.

The meaning of the different options are as follows - note that this can vary a bit between storage engines:

FOR UPGRADEDo a very quick check if the storage format for the table has changed so that one needs to do a REPAIR. This is only needed when one upgrades between major versions of MariaDB or MySQL. This is usually done by running mysql_upgrade.
FASTOnly check tables that has not been closed properly or are marked as corrupt. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally
CHANGEDCheck only tables that has changed since last REPAIR / CHECK. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally.
QUICKDo a fast check. For MyISAM and Aria engine this means we skip checking the delete link chain which may take some time.
MEDIUMScan also the data files. Checks integrity between data and index files with checksums. In most cases this should find all possible errors.
EXTENDEDDoes a full check to verify every possible error. For MyISAM and Aria we verify for each row that all it keys exists and points to the row. This may take a long time on big tables!

For most cases running CHECK TABLE without options or MEDIUM should be good enough.

The Aria storage engine supports progress reporting for this statement.

If you want to know if two tables are identical, take a look at CHECKSUM TABLE.

InnoDB

If CHECK TABLE finds an error in an InnoDB table, MariaDB might shutdown to prevent the error propagation. In this case, the problem will be reported in the error log. Otherwise the table or an index might be marked as corrupted, to prevent use. This does not happen with some minor problems, like a wrong number of entries in a secondary index. Those problems are reported in the output of CHECK TABLE.

Each tablespace contains a header with metadata. This header is not checked by this statement.

During the execution of CHECK TABLE, other threads may be blocked.

1.1.2.1.5 CHECK VIEW

Syntax

CHECK VIEW view_name

Description

The CHECK VIEW statement was introduced in MariaDB 10.0.18 to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use.

See Also

1.1.2.1.6 CHECKSUM TABLE

Syntax

CHECKSUM TABLE tbl_name [, tbl_name] ... [ QUICK | EXTENDED ]

Description

CHECKSUM TABLE reports a table checksum. This is very useful if you want to know if two tables are the same (for example on a master and slave).

With QUICK, the live table checksum is reported if it is available, or NULL otherwise. This is very fast. A live checksum is enabled by specifying the CHECKSUM=1 table option when you create the table; currently, this is supported only for Aria and MyISAM tables.

With EXTENDED, the entire table is read row by row and the checksum is calculated. This can be very slow for large tables.

If neither QUICK nor EXTENDED is specified, MariaDB returns a live checksum if the table storage engine supports it and scans the table otherwise.

CHECKSUM TABLE requires the SELECT privilege for the table.

For a nonexistent table, CHECKSUM TABLE returns NULL and generates a warning.

The table row format affects the checksum value. If the row format changes, the checksum will change. This means that when a table created with a MariaDB/MySQL version is upgraded to another version, the checksum value will probably change.

Two identical tables should always match to the same checksum value; however, also for non-identical tables there is a very slight chance that they will return the same value as the hashing algorithm is not completely collision-free.

Differences Between MariaDB and MySQL

CHECKSUM TABLE may give a different result as MariaDB doesn't ignore NULLs in the columns as MySQL 5.1 does (Later MySQL versions should calculate checksums the same way as MariaDB). You can get the 'old style' checksum in MariaDB by starting mysqld with the --old option. Note however that that the MyISAM and Aria storage engines in MariaDB are using the new checksum internally, so if you are using --old, the CHECKSUM command will be slower as it needs to calculate the checksum row by row.

1.1.2.1.7 CREATE TABLE

Syntax

CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name (create_definition,...) [table_options ]... [partition_options] CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name [(create_definition,...)] [table_options ]... [partition_options] select_statement CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name { LIKE old_table_name | (LIKE old_table_name) }

select_statement: [IGNORE | REPLACE] [AS] SELECT ... (Some legal select statement)

Description

Use the CREATE TABLE statement to create a table with the given name.

In its most basic form, the CREATE TABLE statement provides a table name followed by a list of columns, indexes, and constraints. By default, the table is created in the default database. Specify a database with db_name.tbl_name. If you quote the table name, you must quote the database name and table name separately as `db_name`.`tbl_name`. This is particularly useful for CREATE TABLE ... SELECT, because it allows to create a table into a database, which contains data from other databases. See Identifier Qualifiers.

If a table with the same name exists, error 1050 results. Use IF NOT EXISTS to suppress this error and issue a note instead. Use SHOW WARNINGS to see notes.

The CREATE TABLE statement automatically commits the current transaction, except when using the TEMPORARY keyword.

For valid identifiers to use as table names, see Identifier Names.

Note: if the default_storage_engine is set to ColumnStore then it needs setting on all UMs. Otherwise when the tables using the default engine are replicated across UMs they will use the wrong engine. You should therefore not use this option as a session variable with ColumnStore.

Microsecond precision can be between 0-6. If no precision is specified it is assumed to be 0, for backward compatibility reasons.

Privileges

Executing the CREATE TABLE statement requires the CREATE privilege for the table or the database.

CREATE OR REPLACE

If the OR REPLACE clause is used and the table already exists, then instead of returning an error, the server will drop the existing table and replace it with the newly defined table.

This syntax was originally added to make replication more robust if it has to rollback and repeat statements such as CREATE ... SELECT on replicas.

CREATE OR REPLACE TABLE table_name (a int);

is basically the same as:

DROP TABLE IF EXISTS table_name;
CREATE TABLE table_name (a int);

with the following exceptions:

  • If table_name was locked with LOCK TABLES it will continue to be locked after the statement.
  • Temporary tables are only dropped if the TEMPORARY keyword was used. (With DROP TABLE, temporary tables are preferred to be dropped before normal tables).

Things to be Aware of With CREATE OR REPLACE

  • The table is dropped first (if it existed), after that the CREATE is done. Because of this, if the CREATE fails, then the table will not exist anymore after the statement. If the table was used with LOCK TABLES it will be unlocked.
  • One can't use OR REPLACE together with IF EXISTS.
  • Slaves in replication will by default use CREATE OR REPLACE when replicating CREATE statements that don''t use IF EXISTS. This can be changed by setting the variable slave-ddl-exec-mode to STRICT.

CREATE TABLE IF NOT EXISTS

If the IF NOT EXISTS clause is used, then the table will only be created if a table with the same name does not already exist. If the table already exists, then a warning will be triggered by default.

CREATE TEMPORARY TABLE

Use the TEMPORARY keyword to create a temporary table that is only available to the current session. Temporary tables are dropped when the session ends. Temporary table names are specific to the session. They will not conflict with other temporary tables from other sessions even if they share the same name. They will shadow names of non-temporary tables or views, if they are identical. A temporary table can have the same name as a non-temporary table which is located in the same database. In that case, their name will reference the temporary table when used in SQL statements. You must have the CREATE TEMPORARY TABLES privilege on the database to create temporary tables. If no storage engine is specified, the default_tmp_storage_engine setting will determine the engine.

ROCKSDB temporary tables cannot be created by setting the default_tmp_storage_engine system variable, or using CREATE TEMPORARY TABLE LIKE. Before MariaDB 10.7, they could be specified, but would silently fail, and a MyISAM table would be created instead. From MariaDB 10.7 an error is returned. Explicitly creating a temporary table with ENGINE=ROCKSDB has never been permitted.

CREATE TABLE ... LIKE

Use the LIKE clause instead of a full table definition to create a table with the same definition as another table, including columns, indexes, and table options. Foreign key definitions, as well as any DATA DIRECTORY or INDEX DIRECTORY table options specified on the original table, will not be created.

CREATE TABLE ... SELECT

You can create a table containing data from other tables using the CREATE ... SELECT statement. Columns will be created in the table for each field returned by the SELECT query.

You can also define some columns normally and add other columns from a SELECT. You can also create columns in the normal way and assign them some values using the query, this is done to force a certain type or other field characteristics. The columns that are not named in the query will be placed before the others. For example:

CREATE TABLE test (a INT NOT NULL, b CHAR(10)) ENGINE=MyISAM
    SELECT 5 AS b, c, d FROM another_table;

Remember that the query just returns data. If you want to use the same indexes, or the same columns attributes ([NOT] NULL, DEFAULT, AUTO_INCREMENT) in the new table, you need to specify them manually. Types and sizes are not automatically preserved if no data returned by the SELECT requires the full size, and VARCHAR could be converted into CHAR. The CAST() function can be used to forcee the new table to use certain types.

Aliases (AS) are taken into account, and they should always be used when you SELECT an expression (function, arithmetical operation, etc).

If an error occurs during the query, the table will not be created at all.

If the new table has a primary key or UNIQUE indexes, you can use the IGNORE or REPLACE keywords to handle duplicate key errors during the query. IGNORE means that the newer values must not be inserted an identical value exists in the index. REPLACE means that older values must be overwritten.

If the columns in the new table are more than the rows returned by the query, the columns populated by the query will be placed after other columns. Note that if the strict SQL_MODE is on, and the columns that are not names in the query do not have a DEFAULT value, an error will raise and no rows will be copied.

Concurrent inserts are not used during the execution of a CREATE ... SELECT.

If the table already exists, an error similar to the following will be returned:

ERROR 1050 (42S01): Table 't' already exists

If the IF NOT EXISTS clause is used and the table exists, a note will be produced instead of an error.

To insert rows from a query into an existing table, INSERT ... SELECT can be used.

Column Definitions

create_definition: { col_name column_definition | index_definition | period_definition | CHECK (expr) }

column_definition: data_type [NOT NULL | NULL] [DEFAULT default_value | (expression)] [ON UPDATE [NOW | CURRENT_TIMESTAMP] [(precision)]] [AUTO_INCREMENT] [ZEROFILL] [UNIQUE [KEY] | [PRIMARY] KEY] [INVISIBLE] [{WITH|WITHOUT} SYSTEM VERSIONING] [COMMENT 'string'] [REF_SYSTEM_ID = value] [reference_definition] | data_type [GENERATED ALWAYS] AS { { ROW {START|END} } | { (expression) [VIRTUAL | PERSISTENT | STORED] } } [UNIQUE [KEY]] [COMMENT 'string']

constraint_definition: CONSTRAINT [constraint_name] CHECK (expression)

Note: Until MariaDB 10.4, MariaDB accepts the shortcut format with a REFERENCES clause only in ALTER TABLE and CREATE TABLE statements, but that syntax does nothing. For example:

CREATE TABLE b(for_key INT REFERENCES a(not_key));

MariaDB simply parses it without returning any error or warning, for compatibility with other DBMS's. Before MariaDB 10.2.1 this was also true for CHECK constraints. However, only the syntax described below creates foreign keys.

From MariaDB 10.5, MariaDB will attempt to apply the constraint. See Foreign Keys examples.

Each definition either creates a column in the table or specifies and index or constraint on one or more columns. See Indexes below for details on creating indexes.

Create a column by specifying a column name and a data type, optionally followed by column options. See Data Types for a full list of data types allowed in MariaDB.

NULL and NOT NULL

Use the NULL or NOT NULL options to specify that values in the column may or may not be NULL, respectively. By default, values may be NULL. See also NULL Values in MariaDB.

DEFAULT Column Option

MariaDB starting with 10.2.1

The DEFAULT clause was enhanced in MariaDB 10.2.1. Some enhancements include

  • BLOB and TEXT columns now support DEFAULT.
  • The DEFAULT clause can now be used with an expression or function.

Specify a default value using the DEFAULT clause. If you don't specify DEFAULT then the following rules apply:

  • If the column is not defined with NOT NULL, AUTO_INCREMENT or TIMESTAMP, an explicit DEFAULT NULL will be added. Note that in MySQL and in MariaDB before 10.1.6, you may get an explicit DEFAULT for primary key parts, if not specified with NOT NULL.

The default value will be used if you INSERT a row without specifying a value for that column, or if you specify DEFAULT for that column. Before MariaDB 10.2.1 you couldn't usually provide an expression or function to evaluate at insertion time. You had to provide a constant default value instead. The one exception is that you may use CURRENT_TIMESTAMP as the default value for a TIMESTAMP column to use the current timestamp at insertion time.

CURRENT_TIMESTAMP may also be used as the default value for a DATETIME

From MariaDB 10.2.1 you can use most functions in DEFAULT. Expressions should have parentheses around them. If you use a non deterministic function in DEFAULT then all inserts to the table will be replicated in row mode. You can even refer to earlier columns in the DEFAULT expression (excluding AUTO_INCREMENT columns):

CREATE TABLE t1 (a int DEFAULT (1+1), b int DEFAULT (a+1));
CREATE TABLE t2 (a bigint primary key DEFAULT UUID_SHORT());

The DEFAULT clause cannot contain any stored functions or subqueries, and a column used in the clause must already have been defined earlier in the statement.

Since MariaDB 10.2.1, it is possible to assign BLOB or TEXT columns a DEFAULT value. In earlier versions, assigning a default to these columns was not possible.

MariaDB starting with 10.3.3

Starting from 10.3.3 you can also use DEFAULT (NEXT VALUE FOR sequence)

AUTO_INCREMENT Column Option

Use AUTO_INCREMENT to create a column whose value can can be set automatically from a simple counter. You can only use AUTO_INCREMENT on a column with an integer type. The column must be a key, and there can only be one AUTO_INCREMENT column in a table. If you insert a row without specifying a value for that column (or if you specify 0, NULL, or DEFAULT as the value), the actual value will be taken from the counter, with each insertion incrementing the counter by one. You can still insert a value explicitly. If you insert a value that is greater than the current counter value, the counter is set based on the new value. An AUTO_INCREMENT column is implicitly NOT NULL. Use LAST_INSERT_ID to get the AUTO_INCREMENT value most recently used by an INSERT statement.

ZEROFILL Column Option

If the ZEROFILL column option is specified for a column using a numeric data type, then the column will be set to UNSIGNED and the spaces used by default to pad the field are replaced with zeros. ZEROFILL is ignored in expressions or as part of a UNION. ZEROFILL is a non-standard MySQL and MariaDB enhancement.

PRIMARY KEY Column Option

Use PRIMARY KEY to make a column a primary key. A primary key is a special type of a unique key. There can be at most one primary key per table, and it is implicitly NOT NULL.

Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information.

UNIQUE KEY Column Option

Use UNIQUE KEY (or just UNIQUE) to specify that all values in the column must be distinct from each other. Unless the column is NOT NULL, there may be multiple rows with NULL in the column.

Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information.

COMMENT Column Option

You can provide a comment for each column using the COMMENT clause. The maximum length is 1024 characters. Use the SHOW FULL COLUMNS statement to see column comments.

REF_SYSTEM_ID

REF_SYSTEM_ID can be used to specify Spatial Reference System IDs for spatial data type columns.

Generated Columns

A generated column is a column in a table that cannot explicitly be set to a specific value in a DML query. Instead, its value is automatically generated based on an expression. This expression might generate the value based on the values of other columns in the table, or it might generate the value by calling built-in functions or user-defined functions (UDFs).

There are two types of generated columns:

  • PERSISTENT or STORED: This type's value is actually stored in the table.
  • VIRTUAL: This type's value is not stored at all. Instead, the value is generated dynamically when the table is queried. This type is the default.

Generated columns are also sometimes called computed columns or virtual columns.

For a complete description about generated columns and their limitations, see Generated (Virtual and Persistent/Stored) Columns.

COMPRESSED

MariaDB starting with 10.3.3

Certain columns may be compressed. See Storage-Engine Independent Column Compression.

INVISIBLE

MariaDB starting with 10.3.3

Columns may be made invisible, and hidden in certain contexts. See Invisible Columns.

WITH SYSTEM VERSIONING Column Option

MariaDB starting with 10.3.4

Columns may be explicitly marked as included from system versioning. See System-versioned tables for details.

WITHOUT SYSTEM VERSIONING Column Option

MariaDB starting with 10.3.4

Columns may be explicitly marked as excluded from system versioning. See System-versioned tables for details.

Index Definitions

index_definition: {INDEX|KEY} [index_name] [index_type] (index_col_name,...) [index_option] ... | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name,...) [index_option] ... | [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name,...) reference_definition

index_col_name: col_name [(length)] [ASC | DESC]

index_type: USING {BTREE | HASH | RTREE}

index_option: [ KEY_BLOCK_SIZE [=] value | index_type | WITH PARSER parser_name | COMMENT 'string' | CLUSTERING={YES| NO} ] [ IGNORED | NOT IGNORED ]

reference_definition: REFERENCES tbl_name (index_col_name,...) [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE] [ON DELETE reference_option] [ON UPDATE reference_option]

reference_option: RESTRICT | CASCADE | SET NULL | NO ACTION

INDEX and KEY are synonyms.

Index names are optional, if not specified an automatic name will be assigned. Index name are needed to drop indexes and appear in error messages when a constraint is violated.

Index Categories

Plain Indexes

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

PRIMARY KEY

For PRIMARY KEY indexes, you can specify a name for the index, but it is ignored, and the name of the index is always PRIMARY. From MariaDB 10.3.18 and MariaDB 10.4.8, a warning is explicitly issued if a name is specified. Before then, the name was silently ignored.

See Getting Started with Indexes: Primary Key for more information.

UNIQUE

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

FOREIGN KEY

For FOREIGN KEY indexes, a reference definition must be provided.

For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

First, you have to specify the name of the target (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed:

  • RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300').
  • NO ACTION: Synonym for RESTRICT.
  • CASCADE: The delete/update operation is performed in both tables.
  • SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed).
  • SET DEFAULT: This option is currently implemented only for the PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted.

If either clause is omitted, the default behavior for the omitted clause is RESTRICT.

See Foreign Keys for more information.

FULLTEXT

Use the FULLTEXT keyword to create full-text indexes.

See Full-Text Indexes for more information.

SPATIAL

Use the SPATIAL keyword to create geometric indexes.

See SPATIAL INDEX for more information.

Index Options

KEY_BLOCK_SIZE Index Option

The KEY_BLOCK_SIZE index option is similar to the KEY_BLOCK_SIZE table option.

With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED. However, this does not happen if you just set the KEY_BLOCK_SIZE index option for one or more indexes in the table. The InnoDB storage engine ignores the KEY_BLOCK_SIZE index option. However, the SHOW CREATE TABLE statement may still report it for the index.

For information about the KEY_BLOCK_SIZE index option, see the KEY_BLOCK_SIZE table option below.

Index Types

Each storage engine supports some or all index types. See Storage Engine Index Types for details on permitted index types for each storage engine.

Different index types are optimized for different kind of operations:

  • BTREE is the default type, and normally is the best choice. It is supported by all storage engines. It can be used to compare a column's value with a value using the =, >, >=, <, <=, BETWEEN, and LIKE operators. BTREE can also be used to find NULL values. Searches against an index prefix are possible.
  • HASH is only supported by the MEMORY storage engine. HASH indexes can only be used for =, <=, and >= comparisons. It can not be used for the ORDER BY clause. Searches against an index prefix are not possible.
  • RTREE is the default for SPATIAL indexes, but if the storage engine does not support it BTREE can be used.

Index columns names are listed between parenthesis. After each column, a prefix length can be specified. If no length is specified, the whole column will be indexed. ASC and DESC can be specified for compatibility with are DBMS's, but have no meaning in MariaDB.

WITH PARSER Index Option

The WITH PARSER index option only applies to FULLTEXT indexes and contains the fulltext parser name. The fulltext parser must be an installed plugin.

COMMENT Index Option

A comment of up to 1024 characters is permitted with the COMMENT index option.

The COMMENT index option allows you to specify a comment with user-readable text describing what the index is for. This information is not used by the server itself.

CLUSTERING Index Option

The CLUSTERING index option is only valid for tables using the Tokudb storage engine.

IGNORED / NOT IGNORED

MariaDB starting with 10.6.0

From MariaDB 10.6.0, indexes can be specified to be ignored by the optimizer. See Ignored Indexes.

Periods

MariaDB starting with 10.3.4

period_definition: PERIOD FOR SYSTEM_TIME (start_column_name, end_column_name)

MariaDB supports a subset of the standard syntax for periods. At the moment it's only used for creating System-versioned tables. Both columns must be created, must be either of a TIMESTAMP(6) or BIGINT UNSIGNED type, and be generated as ROW START and ROW END accordingly. See System-versioned tables for details.

The table must also have the WITH SYSTEM VERSIONING clause.

Constraint Expressions

MariaDB starting with 10.2.1

MariaDB 10.2.1 introduced new ways to define a constraint.

Note: Before MariaDB 10.2.1, constraint expressions were accepted in the syntax but ignored.

MariaDB 10.2.1 introduced two ways to define a constraint:

  • CHECK(expression) given as part of a column definition.
  • CONSTRAINT [constraint_name] CHECK (expression)

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraints fails, then the row will not be updated. One can use most deterministic functions in a constraint, including UDFs.

create table t1 (a int check(a>0) ,b int check (b> 0), constraint abc check (a>b));

If you use the second format and you don't give a name to the constraint, then the constraint will get a auto generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name.

One can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL.

See CONSTRAINT for more information.

Table Options

For each individual table you create (or alter), you can set some table options. The general syntax for setting options is:

<OPTION_NAME> = <option_value>, [<OPTION_NAME> = <option_value> ...]

The equal sign is optional.

Some options are supported by the server and can be used for all tables, no matter what storage engine they use; other options can be specified for all storage engines, but have a meaning only for some engines. Also, engines can extend CREATE TABLE with new options.

If the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is enabled, wrong table options generate a warning; otherwise, they generate an error.

table_option: [STORAGE] ENGINE [=] engine_name | AUTO_INCREMENT [=] value | AVG_ROW_LENGTH [=] value | [DEFAULT] CHARACTER SET [=] charset_name | CHECKSUM [=] {0 | 1} | [DEFAULT] COLLATE [=] collation_name | COMMENT [=] 'string' | CONNECTION [=] 'connect_string' | DATA DIRECTORY [=] 'absolute path to directory' | DELAY_KEY_WRITE [=] {0 | 1} | ENCRYPTED [=] {YES | NO} | ENCRYPTION_KEY_ID [=] value | IETF_QUOTES [=] {YES | NO} | INDEX DIRECTORY [=] 'absolute path to directory' | INSERT_METHOD [=] { NO | FIRST | LAST } | KEY_BLOCK_SIZE [=] value | MAX_ROWS [=] value | MIN_ROWS [=] value | PACK_KEYS [=] {0 | 1 | DEFAULT} | PAGE_CHECKSUM [=] {0 | 1} | PAGE_COMPRESSED [=] {0 | 1} | PAGE_COMPRESSION_LEVEL [=] {0 .. 9} | PASSWORD [=] 'string' | ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT|PAGE} | SEQUENCE [=] {0|1} | STATS_AUTO_RECALC [=] {DEFAULT|0|1} | STATS_PERSISTENT [=] {DEFAULT|0|1} | STATS_SAMPLE_PAGES [=] {DEFAULT|value} | TABLESPACE tablespace_name | TRANSACTIONAL [=] {0 | 1} | UNION [=] (tbl_name[,tbl_name]...) | WITH SYSTEM VERSIONING

[STORAGE] ENGINE

[STORAGE] ENGINE specifies a storage engine for the table. If this option is not used, the default storage engine is used instead. That is, the default_storage_engine session option value if it is set, or the value specified for the --default-storage-engine mysqld startup option, or the default storage engine, InnoDB. If the specified storage engine is not installed and active, the default value will be used, unless the NO_ENGINE_SUBSTITUTION SQL MODE is set (default). This is only true for CREATE TABLE, not for ALTER TABLE. For a list of storage engines that are present in your server, issue a SHOW ENGINES.

AUTO_INCREMENT

AUTO_INCREMENT specifies the initial value for the AUTO_INCREMENT primary key. This works for MyISAM, Aria, InnoDB/XtraDB, MEMORY, and ARCHIVE tables. You can change this option with ALTER TABLE, but in that case the new value must be higher than the highest value which is present in the AUTO_INCREMENT column. If the storage engine does not support this option, you can insert (and then delete) a row having the wanted value - 1 in the AUTO_INCREMENT column.

AVG_ROW_LENGTH

AVG_ROW_LENGTH is the average rows size. It only applies to tables using MyISAM and Aria storage engines that have the ROW_FORMAT table option set to FIXED format.

MyISAM uses MAX_ROWS and AVG_ROW_LENGTH to decide the maximum size of a table (default: 256TB, or the maximum file size allowed by the system).

[DEFAULT] CHARACTER SET/CHARSET

[DEFAULT] CHARACTER SET (or [DEFAULT] CHARSET) is used to set a default character set for the table. This is the character set used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default character set will be used. See Setting Character Sets and Collations for details on setting the character sets.

CHECKSUM/TABLE_CHECKSUM

CHECKSUM (or TABLE_CHECKSUM) can be set to 1 to maintain a live checksum for all table's rows. This makes write operations slower, but CHECKSUM TABLE will be very fast. This option is only supported for MyISAM and Aria tables.

[DEFAULT] COLLATE

[DEFAULT] COLLATE is used to set a default collation for the table. This is the collation used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default option will be used. See Setting Character Sets and Collations for details on setting the collations

COMMENT

COMMENT is a comment for the table. The maximum length is 2048 characters. Also used to define table parameters when creating a Spider table.

CONNECTION

CONNECTION is used to specify a server name or a connection string for a Spider, CONNECT, Federated or FederatedX table.

DATA DIRECTORY/INDEX DIRECTORY

DATA DIRECTORY and INDEX DIRECTORY are supported for MyISAM and Aria, and DATA DIRECTORY is also supported by InnoDB if the innodb_file_per_table server system variable is enabled, but only in CREATE TABLE, not in ALTER TABLE. So, carefully choose a path for InnoDB tables at creation time, because it cannot be changed without dropping and re-creating the table. These options specify the paths for data files and index files, respectively. If these options are omitted, the database's directory will be used to store data files and index files. Note that these table options do not work for partitioned tables (use the partition options instead), or if the server has been invoked with the --skip-symbolic-links startup option. To avoid the overwriting of old files with the same name that could be present in the directories, you can use the --keep_files_on_create option (an error will be issued if files already exist). These options are ignored if the NO_DIR_IN_CREATE SQL_MODE is enabled (useful for replication slaves). Also note that symbolic links cannot be used for InnoDB tables.

DATA DIRECTORY works by creating symlinks from where the table would normally have been (inside the datadir) to where the option specifies. For security reasons, to avoid bypassing the privilege system, the server does not permit symlinks inside the datadir. Therefore, DATA DIRECTORY cannot be used to specify a location inside the datadir. An attempt to do so will result in an error 1210 (HY000) Incorrect arguments to DATA DIRECTORY.

DELAY_KEY_WRITE

DELAY_KEY_WRITE is supported by MyISAM and Aria, and can be set to 1 to speed up write operations. In that case, when data are modified, the indexes are not updated until the table is closed. Writing the changes to the index file altogether can be much faster. However, note that this option is applied only if the delay_key_write server variable is set to 'ON'. If it is 'OFF' the delayed index writes are always disabled, and if it is 'ALL' the delayed index writes are always used, disregarding the value of DELAY_KEY_WRITE.

ENCRYPTED

The ENCRYPTED table option can be used to manually set the encryption status of an InnoDB table. See InnoDB Encryption for more information.

Aria does not support the ENCRYPTED table option. See MDEV-18049.

See Data-at-Rest Encryption for more information.

ENCRYPTION_KEY_ID

The ENCRYPTION_KEY_ID table option can be used to manually set the encryption key of an InnoDB table. See InnoDB Encryption for more information.

Aria does not support the ENCRYPTION_KEY_ID table option. See MDEV-18049.

See Data-at-Rest Encryption for more information.

IETF_QUOTES

For the CSV storage engine, the IETF_QUOTES option, when set to YES, enables IETF-compatible parsing of embedded quote and comma characters. Enabling this option for a table improves compatibility with other tools that use CSV, but is not compatible with MySQL CSV tables, or MariaDB CSV tables created without this option. Disabled by default.

INSERT_METHOD

INSERT_METHOD is only used with MERGE tables. This option determines in which underlying table the new rows should be inserted. If you set it to 'NO' (which is the default) no new rows can be added to the table (but you will still be able to perform INSERTs directly against the underlying tables). FIRST means that the rows are inserted into the first table, and LAST means that thet are inserted into the last table.

KEY_BLOCK_SIZE

KEY_BLOCK_SIZE is used to determine the size of key blocks, in bytes or kilobytes. However, this value is just a hint, and the storage engine could modify or ignore it. If KEY_BLOCK_SIZE is set to 0, the storage engine's default value will be used.

With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED.

MIN_ROWS/MAX_ROWS

MIN_ROWS and MAX_ROWS let the storage engine know how many rows you are planning to store as a minimum and as a maximum. These values will not be used as real limits, but they help the storage engine to optimize the table. MIN_ROWS is only used by MEMORY storage engine to decide the minimum memory that is always allocated. MAX_ROWS is used to decide the minimum size for indexes.

PACK_KEYS

PACK_KEYS can be used to determine whether the indexes will be compressed. Set it to 1 to compress all keys. With a value of 0, compression will not be used. With the DEFAULT value, only long strings will be compressed. Uncompressed keys are faster.

PAGE_CHECKSUM

PAGE_CHECKSUM is only applicable to Aria tables, and determines whether indexes and data should use page checksums for extra safety.

PAGE_COMPRESSED

PAGE_COMPRESSED is used to enable InnoDB page compression for InnoDB tables.

PAGE_COMPRESSION_LEVEL

PAGE_COMPRESSION_LEVEL is used to set the compression level for InnoDB page compression for InnoDB tables. The table must also have the PAGE_COMPRESSED table option set to 1.

Valid values for PAGE_COMPRESSION_LEVEL are 1 (the best speed) through 9 (the best compression), .

PASSWORD

PASSWORD is unused.

RAID_TYPE

RAID_TYPE is an obsolete option, as the raid support has been disabled since MySQL 5.0.

ROW_FORMAT

The ROW_FORMAT table option specifies the row format for the data file. Possible values are engine-dependent.

Supported MyISAM Row Formats

For MyISAM, the supported row formats are:

  • FIXED
  • DYNAMIC
  • COMPRESSED

The COMPRESSED row format can only be set by the myisampack command line tool.

See MyISAM Storage Formats for more information.

Supported Aria Row Formats

For Aria, the supported row formats are:

  • PAGE
  • FIXED
  • DYNAMIC.

See Aria Storage Formats for more information.

Supported InnoDB Row Formats

For InnoDB, the supported row formats are:

  • COMPACT
  • REDUNDANT
  • COMPRESSED
  • DYNAMIC.

If the ROW_FORMAT table option is set to FIXED for an InnoDB table, then the server will either return an error or a warning depending on the value of the innodb_strict_mode system variable. If the innodb_strict_mode system variable is set to OFF, then a warning is issued, and MariaDB will create the table using the default row format for the specific MariaDB server version. If the innodb_strict_mode system variable is set to ON, then an error will be raised.

See InnoDB Storage Formats for more information.

Other Storage Engines and ROW_FORMAT

Other storage engines do not support the ROW_FORMAT table option.

SEQUENCE

MariaDB starting with 10.3

If the table is a sequence, then it will have the SEQUENCE set to 1.

STATS_AUTO_RECALC

STATS_AUTO_RECALC indicates whether to automatically recalculate persistent statistics (see STATS_PERSISTENT, below) for an InnoDB table. If set to 1, statistics will be recalculated when more than 10% of the data has changed. When set to 0, stats will be recalculated only when an ANALYZE TABLE is run. If set to DEFAULT, or left out, the value set by the innodb_stats_auto_recalc system variable applies. See InnoDB Persistent Statistics.

STATS_PERSISTENT

STATS_PERSISTENT indicates whether the InnoDB statistics created by ANALYZE TABLE will remain on disk or not. It can be set to 1 (on disk), 0 (not on disk, the pre-MariaDB 10 behavior), or DEFAULT (the same as leaving out the option), in which case the value set by the innodb_stats_persistent system variable will apply. Persistent statistics stored on disk allow the statistics to survive server restarts, and provide better query plan stability. See InnoDB Persistent Statistics.

STATS_SAMPLE_PAGES

STATS_SAMPLE_PAGES indicates how many pages are used to sample index statistics. If 0 or DEFAULT, the default value, the innodb_stats_sample_pages value is used. See InnoDB Persistent Statistics.

TRANSACTIONAL

TRANSACTIONAL is only applicable for Aria tables. In future Aria tables created with this option will be fully transactional, but currently this provides a form of crash protection. See Aria Storage Engine for more details.

UNION

UNION must be specified when you create a MERGE table. This option contains a comma-separated list of MyISAM tables which are accessed by the new table. The list is enclosed between parenthesis. Example: UNION = (t1,t2)

WITH SYSTEM VERSIONING

WITH SYSTEM VERSIONING is used for creating System-versioned tables.

Partitions

partition_options: PARTITION BY { [LINEAR] HASH(expr) | [LINEAR] KEY(column_list) | RANGE(expr) | LIST(expr) | SYSTEM_TIME [INTERVAL time_quantity time_unit] [LIMIT num] } [PARTITIONS num] [SUBPARTITION BY { [LINEAR] HASH(expr) | [LINEAR] KEY(column_list) } [SUBPARTITIONS num] ] [(partition_definition [, partition_definition] ...)]

partition_definition: PARTITION partition_name [VALUES {LESS THAN {(expr) | MAXVALUE} | IN (value_list)}] [[STORAGE] ENGINE [=] engine_name] [COMMENT [=] 'comment_text' ] [DATA DIRECTORY [=] 'data_dir'] [INDEX DIRECTORY [=] 'index_dir'] [MAX_ROWS [=] max_number_of_rows] [MIN_ROWS [=] min_number_of_rows] [TABLESPACE [=] tablespace_name] [NODEGROUP [=] node_group_id] [(subpartition_definition [, subpartition_definition] ...)]

subpartition_definition: SUBPARTITION logical_name [[STORAGE] ENGINE [=] engine_name] [COMMENT [=] 'comment_text' ] [DATA DIRECTORY [=] 'data_dir'] [INDEX DIRECTORY [=] 'index_dir'] [MAX_ROWS [=] max_number_of_rows] [MIN_ROWS [=] min_number_of_rows] [TABLESPACE [=] tablespace_name] [NODEGROUP [=] node_group_id]

If the PARTITION BY clause is used, the table will be partitioned. A partition method must be explicitly indicated for partitions and subpartitions. Partition methods are:

  • [LINEAR] HASH creates a hash key which will be used to read and write rows. The partition function can be any valid SQL expression which returns an INTEGER number. Thus, it is possible to use the HASH method on an integer column, or on functions which accept integer columns as an argument. However, VALUES LESS THAN and VALUES IN clauses can not be used with HASH. An example:
CREATE TABLE t1 (a INT, b CHAR(5), c DATETIME)
    PARTITION BY HASH ( YEAR(c) );

[LINEAR] HASH can be used for subpartitions, too.

  • [LINEAR] KEY is similar to HASH, but the index has an even distribution of data. Also, the expression can only be a column or a list of columns. VALUES LESS THAN and VALUES IN clauses can not be used with KEY.
  • RANGE partitions the rows using on a range of values, using the VALUES LESS THAN operator. VALUES IN is not allowed with RANGE. The partition function can be any valid SQL expression which returns a single value.
  • LIST assigns partitions based on a table's column with a restricted set of possible values. It is similar to RANGE, but VALUES IN must be used for at least 1 columns, and VALUES LESS THAN is disallowed.
  • SYSTEM_TIME partitioning is used for System-versioned tables to store historical data separately from current data.

Only HASH and KEY can be used for subpartitions, and they can be [LINEAR].

It is possible to define up to 1024 partitions and subpartitions.

The number of defined partitions can be optionally specified as PARTITION count. This can be done to avoid specifying all partitions individually. But you can also declare each individual partition and, additionally, specify a PARTITIONS count clause; in the case, the number of PARTITIONs must equal count.

Also see Partitioning Types Overview.

Sequences

MariaDB starting with 10.3

CREATE TABLE can also be used to create a SEQUENCE. See CREATE SEQUENCE and Sequence Overview.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL. CREATE TABLE is atomic, except for CREATE OR REPLACE, which is only crash safe.

Examples

create table if not exists test (
a bigint auto_increment primary key,
name varchar(128) charset utf8,
key name (name(32))
) engine=InnoDB default charset latin1;

This example shows a couple of things:

  • Usage of IF NOT EXISTS; If the table already existed, it will not be created. There will not be any error for the client, just a warning.
  • How to create a PRIMARY KEY that is automatically generated.
  • How to specify a table-specific character set and another for a column.
  • How to create an index (name) that is only partly indexed (to save space).

The following clauses will work from MariaDB 10.2.1 only.

CREATE TABLE t1(
  a int DEFAULT (1+1),
  b int DEFAULT (a+1),
  expires DATETIME DEFAULT(NOW() + INTERVAL 1 YEAR),
  x BLOB DEFAULT USER()
);

See Also

1.1.2.1.8 DELETE

Syntax

Single-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] 
  FROM tbl_name [PARTITION (partition_list)]
  [FOR PORTION OF period FROM expr1 TO expr2]
  [WHERE where_condition]
  [ORDER BY ...]
  [LIMIT row_count]
  [RETURNING select_expr 
    [, select_expr ...]]

Multiple-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    tbl_name[.*] [, tbl_name[.*]] ...
    FROM table_references
    [WHERE where_condition]

Or:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    FROM tbl_name[.*] [, tbl_name[.*]] ...
    USING table_references
    [WHERE where_condition]

Trimming history:

DELETE HISTORY
  FROM tbl_name [PARTITION (partition_list)]
  [BEFORE SYSTEM_TIME [TIMESTAMP|TRANSACTION] expression]

Description

OptionDescription
LOW_PRIORITYWait until all SELECT's are done before starting the statement. Used with storage engines that uses table locking (MyISAM, Aria etc). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.
QUICKSignal the storage engine that it should expect that a lot of rows are deleted. The storage engine engine can do things to speed up the DELETE like ignoring merging of data blocks until all rows are deleted from the block (instead of when a block is half full). This speeds up things at the expanse of lost space in data blocks. At least MyISAM and Aria support this feature.
IGNOREDon't stop the query even if a not-critical error occurs (like data overflow). See How IGNORE works for a full description.

For the single-table syntax, the DELETE statement deletes rows from tbl_name and returns a count of the number of deleted rows. This count can be obtained by calling the ROW_COUNT() function. The WHERE clause, if given, specifies the conditions that identify which rows to delete. With no WHERE clause, all rows are deleted. If the ORDER BY clause is specified, the rows are deleted in the order that is specified. The LIMIT clause places a limit on the number of rows that can be deleted.

For the multiple-table syntax, DELETE deletes from each tbl_name the rows that satisfy the conditions. In this case, ORDER BY and LIMIT> cannot be used. A DELETE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax.

where_condition is an expression that evaluates to true for each row to be deleted. It is specified as described in SELECT.

Currently, you cannot delete from a table and select from the same table in a subquery.

You need the DELETE privilege on a table to delete rows from it. You need only the SELECT privilege for any columns that are only read, such as those named in the WHERE clause. See GRANT.

As stated, a DELETE statement with no WHERE clause deletes all rows. A faster way to do this, when you do not need to know the number of deleted rows, is to use TRUNCATE TABLE. However, within a transaction or if you have a lock on the table, TRUNCATE TABLE cannot be used whereas DELETE can. See TRUNCATE TABLE, and LOCK.

PARTITION

See Partition Pruning and Selection for details.

FOR PORTION OF

RETURNING

It is possible to return a resultset of the deleted rows for a single table to the client by using the syntax DELETE ... RETURNING select_expr [, select_expr2 ...]]

Any of SQL expression that can be calculated from a single row fields is allowed. Subqueries are allowed. The AS keyword is allowed, so it is possible to use aliases.

The use of aggregate functions is not allowed. RETURNING cannot be used in multi-table DELETEs.

MariaDB starting with 10.3.1

Same Source and Target Table

Until MariaDB 10.3.1, deleting from a table with the same source and target was not possible. From MariaDB 10.3.1, this is now possible. For example:

DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0);
MariaDB starting with 10.3.4

DELETE HISTORY

One can use DELETE HISTORY to delete historical information from System-versioned tables.

Examples

How to use the ORDER BY and LIMIT clauses:

DELETE FROM page_hit ORDER BY timestamp LIMIT 1000000;

How to use the RETURNING clause:

DELETE FROM t RETURNING f1;
+------+
| f1   |
+------+
|    5 |
|   50 |
|  500 |
+------+ 

The following statement joins two tables: one is only used to satisfy a WHERE condition, but no row is deleted from it; rows from the other table are deleted, instead.

DELETE post FROM blog INNER JOIN post WHERE blog.id = post.blog_id;

Deleting from the Same Source and Target

CREATE TABLE t1 (c1 INT, c2 INT);
DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0);

Until MariaDB 10.3.1, this returned:

ERROR 1093 (HY000): Table 't1' is specified twice, both as a target for 'DELETE' 
  and as a separate source for

From MariaDB 10.3.1:

Query OK, 0 rows affected (0.00 sec)

See Also

1.1.2.1.9 DROP TABLE

Syntax

DROP [TEMPORARY] TABLE [IF EXISTS] [/*COMMENT TO SAVE*/]
    tbl_name [, tbl_name] ...
    [WAIT n|NOWAIT]
    [RESTRICT | CASCADE]

Description

DROP TABLE removes one or more tables. You must have the DROP privilege for each table. All table data and the table definition are removed, as well as triggers associated to the table, so be careful with this statement! If any of the tables named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist.

Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT.

If another thread is using the table in an explicit transaction or an autocommit transaction, then the thread acquires a metadata lock (MDL) on the table. The DROP TABLE statement will wait in the "Waiting for table metadata lock" thread state until the MDL is released. MDLs are released in the following cases:

  • If an MDL is acquired in an explicit transaction, then the MDL will be released when the transaction ends.
  • If an MDL is acquired in an autocommit transaction, then the MDL will be released when the statement ends.
  • Transactional and non-transactional tables are handled the same.

Note that for a partitioned table, DROP TABLE permanently removes the table definition, all of its partitions, and all of the data which was stored in those partitions. It also removes the partitioning definition (.par) file associated with the dropped table.

For each referenced table, DROP TABLE drops a temporary table with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary table with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary table will not accidentally be dropped.

Use IF EXISTS to prevent an error from occurring for tables that do not exist. A NOTE is generated for each non-existent table when using IF EXISTS. See SHOW WARNINGS.

If a foreign key references this table, the table cannot be dropped. In this case, it is necessary to drop the foreign key first.

RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing.

The comment before the table names (/*COMMENT TO SAVE*/) is stored in the binary log. That feature can be used by replication tools to send their internal messages.

It is possible to specify table names as db_name.tab_name. This is useful to delete tables from multiple databases with one statement. See Identifier Qualifiers for details.

The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session.

Note: DROP TABLE automatically commits the current active transaction, unless you use the TEMPORARY keyword.

MariaDB starting with 10.5.4

From MariaDB 10.5.4, DROP TABLE reliably deletes table remnants inside a storage engine even if the .frm file is missing. Before then, a missing .frm file would result in the statement failing.

MariaDB starting with 10.3.1

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

DROP TABLE in replication

DROP TABLE has the following characteristics in replication:

  • DROP TABLE IF EXISTS are always logged.
  • DROP TABLE without IF EXISTS for tables that don't exist are not written to the binary log.
  • Dropping of TEMPORARY tables are prefixed in the log with TEMPORARY. These drops are only logged when running statement or mixed mode replication.
  • One DROP TABLE statement can be logged with up to 3 different DROP statements:
    • DROP TEMPORARY TABLE list_of_non_transactional_temporary_tables
    • DROP TEMPORARY TABLE list_of_transactional_temporary_tables
    • DROP TABLE list_of_normal_tables

Starting from MariaDB 10.0.8, DROP TABLE on the master is treated on the slave as DROP TABLE IF EXISTS. You can change that by setting slave-ddl-exec-mode to STRICT.

Dropping an Internal #sql-... Table

From MariaDB 10.6, DROP TABLE is atomic and the following does not apply. Until MariaDB 10.5, if the mariadbd/mysqld process is killed during an ALTER TABLE you may find a table named #sql-... in your data directory. In MariaDB 10.3, InnoDB tables with this prefix will be deleted automatically during startup. From MariaDB 10.4, these temporary tables will always be deleted automatically.

If you want to delete one of these tables explicitly you can do so by using the following syntax:

DROP TABLE `#mysql50##sql-...`;

When running an ALTER TABLE…ALGORITHM=INPLACE that rebuilds the table, InnoDB will create an internal #sql-ib table. Until MariaDB 10.3.2, for these tables, the .frm file will be called something else. In order to drop such a table after a server crash, you must rename the #sql*.frm file to match the #sql-ib*.ibd file.

From MariaDB 10.3.3, the same name as the .frm file is used for the intermediate copy of the table. The #sql-ib names are used by TRUNCATE and delayed DROP.

From MariaDB 10.2.19 and MariaDB 10.3.10, the #sql-ib tables will be deleted automatically.

Dropping All Tables in a Database

The best way to drop all tables in a database is by executing DROP DATABASE, which will drop the database itself, and all tables in it.

However, if you want to drop all tables in the database, but you also want to keep the database itself and any other non-table objects in it, then you would need to execute DROP TABLE to drop each individual table. You can construct these DROP TABLE commands by querying the TABLES table in the information_schema database. For example:

SELECT CONCAT('DROP TABLE IF EXISTS `', TABLE_SCHEMA, '`.`', TABLE_NAME, '`;')
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'mydb';

Atomic DROP TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, DROP TABLE for a single table is atomic (MDEV-25180) for most engines, including InnoDB, MyRocks, MyISAM and Aria.

This means that if there is a crash (server down or power outage) during DROP TABLE, all tables that have been processed so far will be completely dropped, including related trigger files and status entries, and the binary log will include a DROP TABLE statement for the dropped tables. Tables for which the drop had not started will be left intact.

In older MariaDB versions, there was a small chance that, during a server crash happening in the middle of DROP TABLE, some storage engines that were using multiple storage files, like MyISAM, could have only a part of its internal files dropped.

In MariaDB 10.5, DROP TABLE was extended to be able to delete a table that was only partly dropped (MDEV-11412) as explained above. Atomic DROP TABLE is the final piece to make DROP TABLE fully reliable.

Dropping multiple tables is crash-safe.

See Atomic DDL for more information.

Examples

DROP TABLE Employees, Customers;

Notes

Beware that DROP TABLE can drop both tables and sequences. This is mainly done to allow old tools like mysqldump to work with sequences.

See Also

1.1.2.1.10 Installing System Tables (mysql_install_db)

mysql_install_db initializes the MariaDB data directory and creates the system tables in the mysql database, if they do not exist. MariaDB uses these tables to manage privileges, roles, and plugins. It also uses them to provide the data for the help command in the mysql client.

mysql_install_db works by starting MariaDB Server's mysqld process in --bootstrap mode and sending commands to create the system tables and their content.

There is a version specifically for Windows, mysql_install_db.exe.

To invoke mysql_install_db, use the following syntax:

mysql_install_db --user=mysql

For the options supported by mysql_install_db, see mysql_install_db: Options.

For the option groups read by mysql_install_db, see mysql_install_db: Option Groups.

See mysql_install_db: Installing System Tables for information on the installation process.

See mysql_install_db: Troubleshooting Issues for information on how to troubleshoot the installation process.

See also:

1.1.2.1.11 mysqlcheck

MariaDB starting with 10.4.6

From MariaDB 10.4.6, mariadb-check is a symlink to mysqlcheck.

MariaDB starting with 10.5.2

From MariaDB 10.5.2, mariadb-check is the name of the tool, with mysqlcheck a symlink .

mysqlcheck is a maintenance tool that allows you to check, repair, analyze and optimize multiple tables from the command line.

It is essentially a commandline interface to the CHECK TABLE, REPAIR TABLE, ANALYZE TABLE and OPTIMIZE TABLE commands, and so, unlike myisamchk and aria_chk, requires the server to be running.

This tool does not work with partitioned tables.

Using mysqlcheck

./client/mysqlcheck [OPTIONS] database [tables]

OR

./client/mysqlcheck [OPTIONS] --databases DB1 [DB2 DB3...]

OR

./client/mysqlcheck [OPTIONS] --all-databases

mysqlcheck can be used to CHECK (-c, -m, -C), REPAIR (-r), ANALYZE (-a), or OPTIMIZE (-o) tables. Some of the options (like -e or -q) can be used at the same time. Not all options are supported by all storage engines.

The -c, -r, -a and -o options are exclusive to each other.

The option --check will be used by default, if no other options were specified. You can change the default behavior by making a symbolic link to the binary, or copying it somewhere with another name, the alternatives are:

mysqlrepairThe default option will be -r (--repair)
mysqlanalyzeThe default option will be -a (--analyze)
mysqloptimizeThe default option will be -o (--optimize)

Options

mysqlcheck supports the following options:

OptionDescription
-A, --all-databasesCheck all the databases. This is the same as --databases with all databases selected.
-1, --all-in-1Instead of issuing one query for each table, use one query per database, naming all tables in the database in a comma-separated list.
-a, --analyzeAnalyze given tables.
--auto-repairIf a checked table is corrupted, automatically fix it. Repairing will be done after all tables have been checked.
--character-sets-dir=nameDirectory where character set files are installed.
-c, --checkCheck table for errors.
-C, --check-only-changedCheck only tables that have changed since last check or haven't been closed properly.
-g, --check-upgradeCheck tables for version-dependent changes. May be used with --auto-repair to correct tables requiring version-dependent updates. Automatically enables the --fix-db-names and --fix-table-names options. Used when upgrading
--compressCompress all information sent between the client and server if both support compression.
-B, --databasesCheck several databases. Note that normally mysqlcheck treats the first argument as a database name, and following arguments as table names. With this option, no tables are given, and all name arguments are regarded as database names.
-# , --debug[=name]Output debug log. Often this is 'd:t:o,filename'.
--debug-checkCheck memory and open file usage at exit.
--debug-infoPrint some debug info at exit.
--default-auth=pluginDefault authentication client-side plugin to use.
--default-character-set=nameSet the default character set.
-e, --extendedIf you are using this option with --check, it will ensure that the table is 100 percent consistent, but will take a long time. If you are using this option with --repair, it will force using the old, slow, repair with keycache method, instead of the much faster repair by sorting.
-F, --fastCheck only tables that haven't been closed properly.
--fix-db-namesConvert database names to the format used since MySQL 5.1. Only database names that contain special characters are affected. Used when upgrading from an old MySQL version.
--fix-table-namesConvert table names (including views) to the format used since MySQL 5.1. Only table names that contain special characters are affected. Used when upgrading from an old MySQL version.
--flushFlush each table after check. This is useful if you don't want to have the checked tables take up space in the caches after the check.
-f, --forceContinue even if we get an SQL error.
-?, --helpDisplay this help message and exit.
-h name, --host=nameConnect to the given host.
-m, --medium-checkFaster than extended-check, but only finds 99.99 percent of all errors. Should be good enough for most cases.
-o, --optimizeOptimize tables.
-p, --password[=name]Password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, mysqlcheck prompts for one. Specifying a password on the command line should be considered insecure. You can use an option file to avoid giving the password on the command line.
-Z, --persistentWhen using ANALYZE TABLE (--analyze), uses the PERSISTENT FOR ALL option, which forces Engine-independent Statistics for this table to be updated. Added in MariaDB 10.1.10
-W, --pipeOn Windows, connect to the server via a named pipe. This option applies only if the server supports named-pipe connections.
--plugin-dirDirectory for client-side plugins.
-P num, --port=numPort number to use for connection or 0 for default to, in order of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default (3306).
--process-tablesPerform the requested operation (check, repair, analyze, optimize) on tables. Enabled by default. Use --skip-process-tables to disable. Added in MariaDB 10.0.18 and MariaDB 5.5.43.
--process-views[=val]Perform the requested operation (only CHECK VIEW or REPAIR VIEW). Possible values are NO, YES (correct the checksum, if necessary, add the mariadb-version field), UPGRADE_FROM_MYSQL (same as YES and toggle the algorithm MERGE<->TEMPTABLE. Added in MariaDB 10.0.18 and MariaDB 5.5.43.
--protocol=nameThe connection protocol (tcp, socket, pipe, memory) to use for connecting to the server. Useful when other connection parameters would cause a protocol to be used other than the one you want.
-q, --quickIf you are using this option with CHECK TABLE, it prevents the check from scanning the rows to check for wrong links. This is the fastest check. If you are using this option with REPAIR TABLE, it will try to repair only the index tree. This is the fastest repair method for a table.
-r, --repairCan fix almost anything except unique keys that aren't unique.
--shared-memory-base-nameShared-memory name to use for Windows connections using shared memory to a local server (started with the --shared-memory option). Case-sensitive.
-s, --silentPrint only error messages.
--skip-databaseDon't process the database (case-sensitive) specified as argument.
-S name, --socket=nameFor connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use.
--sslEnables TLS. TLS is also enabled even without setting this option when certain other TLS options are set. Starting with MariaDB 10.2, the --ssl option will not enable verifying the server certificate by default. In order to verify the server certificate, the user must specify the --ssl-verify-server-cert option.
--ssl-ca=nameDefines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path. See Secure Connections Overview: Certificate Authorities (CAs) for more information. This option implies the --ssl option.
--ssl-capath=nameDefines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. See Secure Connections Overview: Certificate Authorities (CAs) for more information. This option is only supported if the client was built with OpenSSL or yaSSL. If the client was built with GnuTLS or Schannel, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms. This option implies the --ssl option.
--ssl-cert=nameDefines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the --ssl option.
--ssl-cipher=nameList of permitted ciphers or cipher suites to use for TLS. This option implies the --ssl option.
--ssl-crl=nameDefines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path. See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. This option is only supported if the client was built with OpenSSL or Schannel. If the client was built with yaSSL or GnuTLS, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
--ssl-crlpath=nameDefines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. This option is only supported if the client was built with OpenSSL. If the client was built with yaSSL, GnuTLS, or Schannel, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
--ssl-key=nameDefines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the --ssl option.
--ssl-verify-server-certEnables server certificate verification. This option is disabled by default.
--tablesOverrides the --databases or -B option such that all name arguments following the option are regarded as table names.
--use-frmFor repair operations on MyISAM tables, get table structure from .frm file, so the table can be repaired even if the .MYI header is corrupted.
-u, --user=nameUser for login if not current user.
-v, --verbosePrint info about the various stages. You can give this option several times to get even more information. See mysqlcheck and verbose, below.
-V, --versionOutput version information and exit.
--write-binlogWrite ANALYZE, OPTIMIZE and REPAIR TABLE commands to the binary log. Enabled by default; use --skip-write-binlog when commands should not be sent to replication slaves.

Option Files

In addition to reading options from the command-line, mysqlcheck can also read options from option files. If an unknown option is provided to mysqlcheck in an option file, then it is ignored.

The following options relate to how MariaDB command-line tools handles option files. They must be given as the first argument on the command-line:

OptionDescription
--print-defaultsPrint the program argument list and exit.
--no-defaultsDon't read default options from any option file.
--defaults-file=# Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=# In addition to the default option groups, also read option groups with this suffix.

In MariaDB 10.2 and later, mysqlcheck is linked with MariaDB Connector/C. However, MariaDB Connector/C does not yet handle the parsing of option files for this client. That is still performed by the server option file parsing code. See MDEV-19035 for more information.

Option Groups

mysqlcheck reads options from the following option groups from option files:

GroupDescription
[mysqlcheck] Options read by mysqlcheck, which includes both MariaDB Server and MySQL Server.
[mariadb-check]Options read by mysqlcheck. Available starting with MariaDB 10.4.6.
[client] Options read by all MariaDB and MySQL client programs, which includes both MariaDB and MySQL clients. For example, mysqldump.
[client-server]Options read by all MariaDB client programs and the MariaDB Server. This is useful for options like socket and port, which is common between the server and the clients.
[client-mariadb]Options read by all MariaDB client programs.

Notes

Default Values

To see the default values for the options and also to see the arguments you get from configuration files you can do:

./client/mysqlcheck --print-defaults
./client/mysqlcheck --help

mysqlcheck and auto-repair

When running mysqlcheck with --auto-repair (as done by mysql_upgrade), mysqlcheck will first check all tables and then in a separate phase repair those that failed the check.

mysqlcheck and all-databases

mysqlcheck --all-databases will ignore the internal log tables general_log and slow_log as these can't be checked, repaired or optimized.

mysqlcheck and verbose

Using one --verbose option will give you more information about what mysqlcheck is doing.

Using two --verbose options will also give you connection information.

MariaDB starting with 10.0.14

If you use three --verbose options you will also get, on stdout, all ALTER, RENAME, and CHECK commands that mysqlcheck executes.

1.1.2.1.12 OPTIMIZE TABLE

Syntax

OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE
    tbl_name [, tbl_name] ...
    [WAIT n | NOWAIT]

Description

OPTIMIZE TABLE has two main functions. It can either be used to defragment tables, or to update the InnoDB fulltext index.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Defragmenting

OPTIMIZE TABLE works for InnoDB (before MariaDB 10.1.1, only if the innodb_file_per_table server system variable is set), Aria, MyISAM and ARCHIVE tables, and should be used if you have deleted a large part of a table or if you have made many changes to a table with variable-length rows (tables that have VARCHAR, VARBINARY, BLOB, or TEXT columns). Deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions.

This statement requires SELECT and INSERT privileges for the table.

By default, OPTIMIZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, OPTIMIZE TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

OPTIMIZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... OPTIMIZE PARTITION to optimize one or more partitions.

You can use OPTIMIZE TABLE to reclaim the unused space and to defragment the data file. With other storage engines, OPTIMIZE TABLE does nothing by default, and returns this message: " The storage engine for the table doesn't support optimize". However, if the server has been started with the --skip-new option, OPTIMIZE TABLE is linked to ALTER TABLE, and recreates the table. This operation frees the unused space and updates index statistics.

The Aria storage engine supports progress reporting for this statement.

If a MyISAM table is fragmented, concurrent inserts will not be performed until an OPTIMIZE TABLE statement is executed on that table, unless the concurrent_insert server system variable is set to ALWAYS.

Updating an InnoDB fulltext index

When rows are added or deleted to an InnoDB fulltext index, the index is not immediately re-organized, as this can be an expensive operation. Change statistics are stored in a separate location . The fulltext index is only fully re-organized when an OPTIMIZE TABLE statement is run.

By default, an OPTIMIZE TABLE will defragment a table. In order to use it to update fulltext index statistics, the innodb_optimize_fulltext_only system variable must be set to 1. This is intended to be a temporary setting, and should be reset to 0 once the fulltext index has been re-organized.

Since fulltext re-organization can take a long time, the innodb_ft_num_word_optimize variable limits the re-organization to a number of words (2000 by default). You can run multiple OPTIMIZE statements to fully re-organize the index.

Defragmenting InnoDB tablespaces

MariaDB 10.1.1 merged the Facebook/Kakao defragmentation patch, allowing one to use OPTIMIZE TABLE to defragment InnoDB tablespaces. For this functionality to be enabled, the innodb_defragment system variable must be enabled. No new tables are created and there is no need to copy data from old tables to new tables. Instead, this feature loads n pages (determined by innodb-defragment-n-pages) and tries to move records so that pages would be full of records and then frees pages that are fully empty after the operation. Note that tablespace files (including ibdata1) will not shrink as the result of defragmentation, but one will get better memory utilization in the InnoDB buffer pool as there are fewer data pages in use.

See Defragmenting InnoDB Tablespaces for more details.

See Also

1.1.2.1.13 RENAME TABLE

Syntax

RENAME TABLE[S] [IF EXISTS] tbl_name 
  [WAIT n | NOWAIT]
  TO new_tbl_name
    [, tbl_name2 TO new_tbl_name2] ...

Description

This statement renames one or more tables or views, but not the privileges associated with them.

IF EXISTS

MariaDB starting with 10.5.2

If this directive is used, one will not get an error if the table to be renamed doesn't exist.

The rename operation is done atomically, which means that no other session can access any of the tables while the rename is running. For example, if you have an existing table old_table, you can create another table new_table that has the same structure but is empty, and then replace the existing table with the empty one as follows (assuming that backup_table does not already exist):

CREATE TABLE new_table (...);
RENAME TABLE old_table TO backup_table, new_table TO old_table;

tbl_name can optionally be specified as db_name.tbl_name. See Identifier Qualifiers. This allows to use RENAME to move a table from a database to another (as long as they are on the same filesystem):

RENAME TABLE db1.t TO db2.t;

Note that moving a table to another database is not possible if it has some triggers. Trying to do so produces the following error:

ERROR 1435 (HY000): Trigger in wrong schema

Also, views cannot be moved to another database:

ERROR 1450 (HY000): Changing schema from 'old_db' to 'new_db' is not allowed.

Multiple tables can be renamed in a single statement. The presence or absence of the optional S (RENAME TABLE or RENAME TABLES) has no impact, whether a single or multiple tables are being renamed.

If a RENAME TABLE renames more than one table and one renaming fails, all renames executed by the same statement are rolled back.

Renames are always executed in the specified order. Knowing this, it is also possible to swap two tables' names:

RENAME TABLE t1 TO tmp_table,
    t2 TO t1,
    tmp_table TO t2;

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

Privileges

Executing the RENAME TABLE statement requires the DROP, CREATE and INSERT privileges for the table or the database.

Atomic RENAME TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, RENAME TABLE is atomic for most engines, including InnoDB, MyRocks, MyISAM and Aria (MDEV-23842). This means that if there is a crash (server down or power outage) during RENAME TABLE, all tables will revert to their original names and any changes to trigger files will be reverted.

In older MariaDB version there was a small chance that, during a server crash happening in the middle of RENAME TABLE, some tables could have been renamed (in the worst case partly) while others would not be renamed.

See Atomic DDL for more information.

1.1.2.1.14 REPAIR TABLE

Syntax

REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE
    tbl_name [, tbl_name] ...
    [QUICK] [EXTENDED] [USE_FRM]

Description

REPAIR TABLE repairs a possibly corrupted table. By default, it has the same effect as

myisamchk --recover tbl_name

or

aria_chk --recover tbl_name

See aria_chk and myisamchk for more.

REPAIR TABLE works for Archive, Aria, CSV and MyISAM tables. For InnoDB, see recovery modes. For CSV, see also Checking and Repairing CSV Tables. For Archive, this statement also improves compression. If the storage engine does not support this statement, a warning is issued.

This statement requires SELECT and INSERT privileges for the table.

By default, REPAIR TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, REPAIR TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

When an index is recreated, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for ALTER TABLE.

REPAIR TABLE is also supported for partitioned tables. However, the USE_FRM option cannot be used with this statement on a partitioned table.

ALTER TABLE ... REPAIR PARTITION can be used to repair one or more partitions.

The Aria storage engine supports progress reporting for this statement.

1.1.2.1.15 REPAIR VIEW

Syntax

REPAIR [NO_WRITE_TO_BINLOG | LOCAL] VIEW  view_name[, view_name] ... [FROM MYSQL]

Description

The REPAIR VIEW statement was introduced to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped compared to their MySQL on disk representation. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use.

By default it corrects the checksum and if necessary adds the mariadb-version field. If the optional FROM MYSQL clause is used, and no mariadb-version field is present, the MERGE and TEMPTABLE algorithms are toggled.

By default, REPAIR VIEW statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

See Also

1.1.2.1.16 REPLACE

Syntax

REPLACE [LOW_PRIORITY | DELAYED]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
[RETURNING select_expr 
      [, select_expr ...]]

Description

REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. If the table has more than one UNIQUE keys, it is possible that the new row conflicts with more than one row. In this case, all conflicting rows will be deleted.

The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use REPLACE ... SELECT to copy rows between different databases.

MariaDB starting with 10.5.0

The RETURNING clause was introduced in MariaDB 10.5.0

Basically it works like this:

BEGIN;
SELECT 1 FROM t1 WHERE key=# FOR UPDATE;
IF found-row
  DELETE FROM t1 WHERE key=# ;
ENDIF
INSERT INTO t1 VALUES (...);
END;

The above can be replaced with:

REPLACE INTO t1 VALUES (...)

REPLACE is a MariaDB/MySQL extension to the SQL standard. It either inserts, or deletes and inserts. For other MariaDB/MySQL extensions to standard SQL --- that also handle duplicate values --- see IGNORE and INSERT ON DUPLICATE KEY UPDATE.

Note that unless the table has a PRIMARY KEY or UNIQUE index, using a REPLACE statement makes no sense. It becomes equivalent to INSERT, because there is no index to be used to determine whether a new row duplicates another.

Values for all columns are taken from the values sSee Partition Pruning and Selection for details.pecified in the REPLACE statement. Any missing columns are set to their default values, just as happens for INSERT. You cannot refer to values from the current row and use them in the new row. If you use an assignment such as 'SET col = col + 1', the reference to the column name on the right hand side is treated as DEFAULT(col), so the assignment is equivalent to 'SET col = DEFAULT(col) + 1'.

To use REPLACE, you must have both the INSERT and DELETE privileges for the table.

There are some gotchas you should be aware of, before using REPLACE:

  • If there is an AUTO_INCREMENT field, a new value will be generated.
  • If there are foreign keys, ON DELETE action will be activated by REPLACE.
  • Triggers on DELETE and INSERT will be activated by REPLACE.

To avoid some of these behaviors, you can use INSERT ... ON DUPLICATE KEY UPDATE.

This statement activates INSERT and DELETE triggers. See Trigger Overview for details.

PARTITION

See Partition Pruning and Selection for details.

REPLACE RETURNING

REPLACE ... RETURNING returns a resultset of the replaced rows.

This returns the listed columns for all the rows that are replaced, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple REPLACE statement

REPLACE INTO t2 VALUES (1,'Leopard'),(2,'Dog') RETURNING id2, id2+id2 
as Total ,id2|id2, id2&&id2;
+-----+-------+---------+----------+
| id2 | Total | id2|id2 | id2&&id2 |
+-----+-------+---------+----------+
|   1 |     2 |       1 |        1 |
|   2 |     4 |       2 |        1 |
+-----+-------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
      RETURN (SELECT arg+arg);
    END|

DELIMITER ;
PREPARE stmt FROM "REPLACE INTO t2 SET id2=3, animal2='Fox' RETURNING f2(id2),
UPPER(animal2)";

EXECUTE stmt;
+---------+----------------+
| f2(id2) | UPPER(animal2) |
+---------+----------------+
|       6 | FOX            |
+---------+----------------+

Subqueries in the statement

REPLACE INTO t1 SELECT * FROM t2 RETURNING (SELECT id2 FROM t2 WHERE 
id2 IN (SELECT id2 FROM t2 WHERE id2=1)) AS new_id;
+--------+
| new_id |
+--------+
|      1 |
|      1 |
|      1 |
|      1 |
+--------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used..

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used, or it can be used in REPLACE...SEL== Description

REPLACE ... RETURNING returns a resultset of the replaced rows.

This returns the listed columns for all the rows that are replaced, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple REPLACE statement

REPLACE INTO t2 VALUES (1,'Leopard'),(2,'Dog') RETURNING id2, id2+id2 
as Total ,id2|id2, id2&&id2;
+-----+-------+---------+----------+
| id2 | Total | id2|id2 | id2&&id2 |
+-----+-------+---------+----------+
|   1 |     2 |       1 |        1 |
|   2 |     4 |       2 |        1 |
+-----+-------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
      RETURN (SELECT arg+arg);
    END|

DELIMITER ;
PREPARE stmt FROM "REPLACE INTO t2 SET id2=3, animal2='Fox' RETURNING f2(id2),
UPPER(animal2)";

EXECUTE stmt;
+---------+----------------+
| f2(id2) | UPPER(animal2) |
+---------+----------------+
|       6 | FOX            |
+---------+----------------+

Subqueries in the statement

REPLACE INTO t1 SELECT * FROM t2 RETURNING (SELECT id2 FROM t2 WHERE 
id2 IN (SELECT id2 FROM t2 WHERE id2=1)) AS new_id;
+--------+
| new_id |
+--------+
|      1 |
|      1 |
|      1 |
|      1 |
+--------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used..

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used, or it can be used in REPLACE...SELECT...RETURNING if the table in the RETURNING clause is not the same as the REPLACE table. ECT...RETURNING if the table in the RETURNING clause is not the same as the REPLACE table.

See Also

1.1.2.1.17 SHOW COLUMNS

Syntax

SHOW [FULL] {COLUMNS | FIELDS} FROM tbl_name [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW COLUMNS displays information about the columns in a given table. It also works for views. The LIKE clause, if present on its own, indicates which column names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

If the data types differ from what you expect them to be based on a CREATE TABLE statement, note that MariaDB sometimes changes data types when you create or alter a table. The conditions under which this occurs are described in the Silent Column Changes article.

The FULL keyword causes the output to include the column collation and comments, as well as the privileges you have for each column.

You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. In other words, these two statements are equivalent:

SHOW COLUMNS FROM mytable FROM mydb;
SHOW COLUMNS FROM mydb.mytable;

SHOW COLUMNS displays the following values for each table column:

Field indicates the column name.

Type indicates the column data type.

Collation indicates the collation for non-binary string columns, or NULL for other columns. This value is displayed only if you use the FULL keyword.

The Null field contains YES if NULL values can be stored in the column, NO if not.

The Key field indicates whether the column is indexed:

  • If Key is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, non-unique index.
  • If Key is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY.
  • If Key is UNI, the column is the first column of a unique-valued index that cannot contain NULL values.
  • If Key is MUL, multiple occurrences of a given value are allowed within the column. The column is the first column of a non-unique index or a unique-valued index that can contain NULL values.

If more than one of the Key values applies to a given column of a table, Key displays the one with the highest priority, in the order PRI, UNI, MUL.

A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is no PRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value.

The Default field indicates the default value that is assigned to the column.

The Extra field contains any additional information that is available about a given column.

ValueDescription
AUTO_INCREMENTThe column was created with the AUTO_INCREMENT keyword.
PERSISTENTThe column was created with the PERSISTENT keyword. (New in 5.3)
VIRTUALThe column was created with the VIRTUAL keyword. (New in 5.3)
on update CURRENT_TIMESTAMPThe column is a TIMESTAMP column that is automatically updated on INSERT and UPDATE.

Privileges indicates the privileges you have for the column. This value is displayed only if you use the FULL keyword.

Comment indicates any comment the column has. This value is displayed only if you use the FULL keyword.

SHOW FIELDS is a synonym for SHOW COLUMNS. Also DESCRIBE and EXPLAIN can be used as shortcuts.

You can also list a table's columns with:

mysqlshow db_name tbl_name

See the mysqlshow command for more details.

The DESCRIBE statement provides information similar to SHOW COLUMNS. The information_schema.COLUMNS table provides similar, but more complete, information.

The SHOW CREATE TABLE, SHOW TABLE STATUS, and SHOW INDEX statements also provide information about tables.

Examples

SHOW COLUMNS FROM city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | NO   |     |         |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | NO   |     | 0       |                |
+------------+----------+------+-----+---------+----------------+
SHOW COLUMNS FROM employees WHERE Type LIKE 'Varchar%';
+---------------+-------------+------+-----+---------+-------+
| Field         | Type        | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| first_name    | varchar(30) | NO   | MUL | NULL    |       |
| last_name     | varchar(40) | NO   |     | NULL    |       |
| position      | varchar(25) | NO   |     | NULL    |       |
| home_address  | varchar(50) | NO   |     | NULL    |       |
| home_phone    | varchar(12) | NO   |     | NULL    |       |
| employee_code | varchar(25) | NO   | UNI | NULL    |       |
+---------------+-------------+------+-----+---------+-------+

See Also

1.1.2.1.18 SHOW CREATE TABLE

Syntax

SHOW CREATE TABLE tbl_name

Description

Shows the CREATE TABLE statement that created the given table. The statement requires the SELECT privilege for the table. This statement also works with views and SEQUENCE.

SHOW CREATE TABLE quotes table and column names according to the value of the sql_quote_show_create server system variable.

Certain SQL_MODE values can result in parts of the original CREATE statement not being included in the output. MariaDB-specific table options, column options, and index options are not included in the output of this statement if the NO_TABLE_OPTIONS, NO_FIELD_OPTIONS and NO_KEY_OPTIONS SQL_MODE flags are used. All MariaDB-specific table attributes are also not shown when a non-MariaDB/MySQL emulation mode is used, which includes ANSI, DB2, POSTGRESQL, MSSQL, MAXDB or ORACLE.

Invalid table options, column options and index options are normally commented out (note, that it is possible to create a table with invalid options, by altering a table of a different engine, where these options were valid). To have them uncommented, enable the IGNORE_BAD_TABLE_OPTIONS SQL_MODE. Remember that replaying a CREATE TABLE statement with uncommented invalid options will fail with an error, unless the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is in effect.

Note that SHOW CREATE TABLE is not meant to provide metadata about a table. It provides information about how the table was declared, but the real table structure could differ a bit. For example, if an index has been declared as HASH, the CREATE TABLE statement returned by SHOW CREATE TABLE will declare that index as HASH; however, it is possible that the index is in fact a BTREE, because the storage engine does not support HASH.

MariaDB starting with 10.2.1

MariaDB 10.2.1 permits TEXT and BLOB data types to be assigned a DEFAULT value. As a result, from MariaDB 10.2.1, SHOW CREATE TABLE will append a DEFAULT NULL to nullable TEXT or BLOB fields if no specific default is provided.

MariaDB starting with 10.2.2

From MariaDB 10.2.2, numbers are no longer quoted in the DEFAULT clause in SHOW CREATE statement. Previously, MariaDB quoted numbers.

Examples

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `s` char(60) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

With sql_quote_show_create off:

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE t (
  id int(11) NOT NULL AUTO_INCREMENT,
  s char(60) DEFAULT NULL,
  PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Unquoted numeric DEFAULTs, from MariaDB 10.2.2:

CREATE TABLE td (link TINYINT DEFAULT 1);

SHOW CREATE TABLE td\G
*************************** 1. row ***************************
       Table: td
Create Table: CREATE TABLE `td` (
  `link` tinyint(4) DEFAULT 1
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Quoted numeric DEFAULTs, until MariaDB 10.2.1:

CREATE TABLE td (link TINYINT DEFAULT 1);

SHOW CREATE TABLE td\G
*************************** 1. row ***************************
       Table: td
Create Table: CREATE TABLE `td` (
  `link` tinyint(4) DEFAULT '1'
) ENGINE=InnoDB DEFAULT CHARSET=latin1

SQL_MODE impacting the output:

SELECT @@sql_mode;
+-------------------------------------------------------------------------------------------+
| @@sql_mode                                                                                |
+-------------------------------------------------------------------------------------------+
| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------------------------------------------------------+

CREATE TABLE `t1` (
       `id` int(11) NOT NULL AUTO_INCREMENT,
       `msg` varchar(100) DEFAULT NULL,
       PRIMARY KEY (`id`)
     ) ENGINE=InnoDB DEFAULT CHARSET=latin1
;

SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `msg` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

SET SQL_MODE=ORACLE;

SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE "t1" (
  "id" int(11) NOT NULL,
  "msg" varchar(100) DEFAULT NULL,
  PRIMARY KEY ("id")

See Also

1.1.2.1.19 SHOW INDEX

Syntax

SHOW {INDEX | INDEXES | KEYS} 
 FROM tbl_name [FROM db_name]
 [WHERE expr]

Description

SHOW INDEX returns table index information. The format resembles that of the SQLStatistics call in ODBC.

You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. These two statements are equivalent:

SHOW INDEX FROM mytable FROM mydb;
SHOW INDEX FROM mydb.mytable;

SHOW KEYS and SHOW INDEXES are synonyms for SHOW INDEX.

You can also list a table's indexes with the mariadb-show/mysqlshow command:

mysqlshow -k db_name tbl_name

The information_schema.STATISTICS table stores similar information.

The following fields are returned by SHOW INDEX.

FieldDescription
TableTable name
Non_unique1 if the index permits duplicate values, 0 if values must be unique.
Key_nameIndex name. The primary key is always named PRIMARY.
Seq_in_indexThe column's sequence in the index, beginning with 1.
Column_nameColumn name.
CollationEither A, if the column is sorted in ascending order in the index, or NULL if it's not sorted.
CardinalityEstimated number of unique values in the index. The cardinality statistics are calculated at various times, and can help the optimizer make improved decisions.
Sub_partNULL if the entire column is included in the index, or the number of included characters if not.
PackedNULL if the index is not packed, otherwise how the index is packed.
NullNULL if NULL values are permitted in the column, an empty string if NULL's are not permitted.
Index_typeThe index type, which can be BTREE, FULLTEXT, HASH or RTREE. See Storage Engine Index Types.
CommentOther information, such as whether the index is disabled.
Index_commentContents of the COMMENT attribute when the index was created.
IgnoredWhether or not an index will be ignored by the optimizer. See Ignored Indexes. From MariaDB 10.6.0.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Examples

CREATE TABLE IF NOT EXISTS `employees_example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(30) NOT NULL,
  `last_name` varchar(40) NOT NULL,
  `position` varchar(25) NOT NULL,
  `home_address` varchar(50) NOT NULL,
  `home_phone` varchar(12) NOT NULL,
  `employee_code` varchar(25) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `employee_code` (`employee_code`),
  KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;

INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`)
  VALUES
  ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'),
  ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'),
  ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'),
  ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'),
  ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'),
  ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1');
SHOW INDEXES FROM employees_example\G
*************************** 1. row ***************************
        Table: employees_example
   Non_unique: 0
     Key_name: PRIMARY
 Seq_in_index: 1
  Column_name: id
    Collation: A
  Cardinality: 6
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 2. row ***************************
        Table: employees_example
   Non_unique: 0
     Key_name: employee_code
 Seq_in_index: 1
  Column_name: employee_code
    Collation: A
  Cardinality: 6
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 3. row ***************************
        Table: employees_example
   Non_unique: 1
     Key_name: first_name
 Seq_in_index: 1
  Column_name: first_name
    Collation: A
  Cardinality: NULL
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 4. row ***************************
        Table: employees_example
   Non_unique: 1
     Key_name: first_name
 Seq_in_index: 2
  Column_name: last_name
    Collation: A
  Cardinality: NULL
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO

See Also

1.1.2.1.20 TRUNCATE TABLE

Syntax

TRUNCATE [TABLE] tbl_name
  [WAIT n | NOWAIT]

Description

TRUNCATE TABLE empties a table completely. It requires the DROP privilege. See GRANT.

tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers).

Logically, TRUNCATE TABLE is equivalent to a DELETE statement that deletes all rows, but there are practical differences under some circumstances.

TRUNCATE TABLE will fail for an InnoDB table if any FOREIGN KEY constraints from other tables reference the table, returning the error:

ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint

Foreign Key constraints between columns in the same table are permitted.

For an InnoDB table, if there are no FOREIGN KEY constraints, InnoDB performs fast truncation by dropping the original table and creating an empty one with the same definition, which is much faster than deleting rows one by one. The AUTO_INCREMENT counter is reset by TRUNCATE TABLE, regardless of whether there is a FOREIGN KEY constraint.

The count of rows affected by TRUNCATE TABLE is accurate only when it is mapped to a DELETE statement.

For other storage engines, TRUNCATE TABLE differs from DELETE in the following ways:

  • Truncate operations drop and re-create the table, which is much faster than deleting rows one by one, particularly for large tables.
  • Truncate operations cause an implicit commit.
  • Truncation operations cannot be performed if the session holds an active table lock.
  • Truncation operations do not return a meaningful value for the number of deleted rows. The usual result is "0 rows affected," which should be interpreted as "no information."
  • As long as the table format file tbl_name.frm is valid, the table can be re-created as an empty table with TRUNCATE TABLE, even if the data or index files have become corrupted.
  • The table handler does not remember the last used AUTO_INCREMENT value, but starts counting from the beginning. This is true even for MyISAM and InnoDB, which normally do not reuse sequence values.
  • When used with partitioned tables, TRUNCATE TABLE preserves the partitioning; that is, the data and index files are dropped and re-created, while the partition definitions (.par) file is unaffected.
  • Since truncation of a table does not make any use of DELETE, the TRUNCATE statement does not invoke ON DELETE triggers.
  • TRUNCATE TABLE will only reset the values in the Performance Schema summary tables to zero or null, and will not remove the rows.

For the purposes of binary logging and replication, TRUNCATE TABLE is treated as DROP TABLE followed by CREATE TABLE (DDL rather than DML).

TRUNCATE TABLE does not work on views. Currently, TRUNCATE TABLE drops all historical records from a system-versioned table.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Oracle-mode

Oracle-mode from MariaDB 10.3 permits the optional keywords REUSE STORAGE or DROP STORAGE to be used.

TRUNCATE [TABLE] tbl_name [{DROP | REUSE} STORAGE] [WAIT n | NOWAIT]

These have no effect on the operation.

Performance

TRUNCATE TABLE is faster than DELETE, because it drops and re-creates a table.

With InnoDB, TRUNCATE TABLE is slower if innodb_file_per_table=ON is set (the default). This is because TRUNCATE TABLE unlinks the underlying tablespace file, which can be an expensive operation. See MDEV-8069 for more details.

The performance issues with innodb_file_per_table=ON can be exacerbated in cases where the InnoDB buffer pool is very large and innodb_adaptive_hash_index=ON is set. In that case, using DROP TABLE followed by CREATE TABLE instead of TRUNCATE TABLE may perform better. Setting innodb_adaptive_hash_index=OFF (it defaults to ON before MariaDB 10.5) can also help. In MariaDB 10.2 only, from MariaDB 10.2.19, this performance can also be improved by setting innodb_safe_truncate=OFF. See MDEV-9459 for more details.

Setting innodb_adaptive_hash_index=OFF can also improve TRUNCATE TABLE performance in general. See MDEV-16796 for more details.

See Also

1.1.2.1.21 UPDATE

Syntax

Single-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_reference 
  [PARTITION (partition_list)]
  [FOR PORTION OF period FROM expr1 TO expr2]
  SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ...
  [WHERE where_condition]
  [ORDER BY ...]
  [LIMIT row_count]

Multiple-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_references
    SET col1={expr1|DEFAULT} [, col2={expr2|DEFAULT}] ...
    [WHERE where_condition]

Description

For the single-table syntax, the UPDATE statement updates columns of existing rows in the named table with new values. The SET clause indicates which columns to modify and the values they should be given. Each value can be given as an expression, or the keyword DEFAULT to set a column explicitly to its default value. The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated.

Until MariaDB 10.3.2, for the multiple-table syntax, UPDATE updates rows in each table named in table_references that satisfy the conditions. In this case, ORDER BY and LIMIT cannot be used. This restriction was lifted in MariaDB 10.3.2 and both clauses can be used with multiple-table updates. An UPDATE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax.

where_condition is an expression that evaluates to true for each row to be updated.

table_references and where_condition are as specified as described in SELECT.

For single-table updates, assignments are evaluated in left-to-right order, while for multi-table updates, there is no guarantee of a particular order. If the SIMULTANEOUS_ASSIGNMENT sql_mode (available from MariaDB 10.3.5) is set, UPDATE statements evaluate all assignments simultaneously.

You need the UPDATE privilege only for columns referenced in an UPDATE that are actually updated. You need only the SELECT privilege for any columns that are read but not modified. See GRANT.

The UPDATE statement supports the following modifiers:

  • If you use the LOW_PRIORITY keyword, execution of the UPDATE is delayed until no other clients are reading from the table. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.
  • If you use the IGNORE keyword, the update statement does not abort even if errors occur during the update. Rows for which duplicate-key conflicts occur are not updated. Rows for which columns are updated to values that would cause data conversion errors are updated to the closest valid values instead.

PARTITION

See Partition Pruning and Selection for details.

FOR PORTION OF

UPDATE Statements With the Same Source and Target

MariaDB starting with 10.3.2

From MariaDB 10.3.2, UPDATE statements may have the same source and target.

For example, given the following table:

DROP TABLE t1;
CREATE TABLE t1 (c1 INT, c2 INT);
INSERT INTO t1 VALUES (10,10), (20,20);

Until MariaDB 10.3.1, the following UPDATE statement would not work:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);
ERROR 1093 (HY000): Table 't1' is specified twice, 
  both as a target for 'UPDATE' and as a separate source for data

From MariaDB 10.3.2, the statement executes successfully:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);

SELECT * FROM t1;
+------+------+
| c1   | c2   |
+------+------+
|   10 |   10 |
|   21 |   20 |
+------+------+

Example

Single-table syntax:

UPDATE table_name SET column1 = value1, column2 = value2 WHERE id=100;

Multiple-table syntax:

UPDATE tab1, tab2 SET tab1.column1 = value1, tab1.column2 = value2 WHERE tab1.id = tab2.id;

See Also

1.1.2.1.22 IGNORE

The IGNORE option tells the server to ignore some common errors.

IGNORE can be used with the following statements:

The logic used:

  • Variables out of ranges are replaced with the maximum/minimum value.
  • SQL_MODEs STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE are ignored.
  • Inserting NULL in a NOT NULL field will insert 0 ( in a numerical field), 0000-00-00 ( in a date field) or an empty string ( in a character field).
  • Rows that cause a duplicate key error or break a foreign key constraint are not inserted, updated, or deleted.

The following errors are ignored:

Error numberSymbolic error nameDescription
1022ER_DUP_KEYCan't write; duplicate key in table '%s'
1048ER_BAD_NULL_ERRORColumn '%s' cannot be null
1062ER_DUP_ENTRYDuplicate entry '%s' for key %d
1242ER_SUBQUERY_NO_1_ROWSubquery returns more than 1 row
1264ER_WARN_DATA_OUT_OF_RANGEOut of range value for column '%s' at row %ld
1265WARN_DATA_TRUNCATEDData truncated for column '%s' at row %ld
1292ER_TRUNCATED_WRONG_VALUETruncated incorrect %s value: '%s'
1366ER_TRUNCATED_WRONG_VALUE_FOR_FIELDIncorrect integer value
1369ER_VIEW_CHECK_FAILEDCHECK OPTION failed '%s.%s'
1451ER_ROW_IS_REFERENCED_2Cannot delete or update a parent row
1452ER_NO_REFERENCED_ROW_2Cannot add or update a child row: a foreign key constraint fails (%s)
1526ER_NO_PARTITION_FOR_GIVEN_VALUETable has no partition for value %s
1586ER_DUP_ENTRY_WITH_KEY_NAMEDuplicate entry '%s' for key '%s'
1591ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENTTable has no partition for some existing values
1748ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SETFound a row not matching the given partition set

Ignored errors normally generate a warning.

A property of the IGNORE clause consists in causing transactional engines and non-transactional engines (like XtraDB and Aria) to behave the same way. For example, normally a multi-row insert which tries to violate a UNIQUE contraint is completely rolled back on XtraDB/InnoDB, but might be partially executed on Aria. With the IGNORE clause, the statement will be partially executed in both engines.

Duplicate key errors also generate warnings. The OLD_MODE server variable can be used to prevent this.

1.1.2.2 ANALYZE and EXPLAIN Statements

1.1.2.2.1 ANALYZE FORMAT=JSON

ANALYZE FORMAT=JSON is a mix of the EXPLAIN FORMAT=JSON and ANALYZE statement features. The ANALYZE FORMAT=JSON $statement will execute $statement, and then print the output of EXPLAIN FORMAT=JSON, amended with data from the query execution.

Basic Execution Data

You can get the following also from tabular ANALYZE statement form:

  • r_rows is provided for any node that reads rows. It shows how many rows were read, on average
  • r_filtered is provided whenever there is a condition that is checked. It shows the percentage of rows left after checking the condition.

Advanced Execution Data

The most important data not available in the regular tabula ANALYZE statement are:

  • r_loops field. This shows how many times the node was executed. Most query plan elements have this field.
  • r_total_time_ms field. It shows how much time in total was spent executing this node. If the node has subnodes, their execution time is included.
  • r_buffer_size field. Query plan nodes that make use of buffers report the size of buffer that was was used.

Data About Individual Query Plan Nodes

  • filesort node reports whether sorting was done with LIMIT n parameter, and how many rows were in the sort result.
  • block-nl-join node has r_loops field, which allows to tell whether Using join buffer was efficient
  • range-checked-for-each-record reports counters that show the result of the check.
  • expression-cache is used for subqueries, and it reports how many times the cache was used, and what cache hit ratio was.
  • union_result node has r_rows so one can see how many rows were produced after UNION operation
  • and so forth

Use Cases

See Examples of ANALYZE FORMAT=JSON.

1.1.2.2.2 ANALYZE FORMAT=JSON Examples

Example #1

Customers who have ordered more than 1M goods.

ANALYZE FORMAT=JSON
SELECT COUNT(*)
FROM customer
WHERE
  (SELECT SUM(o_totalprice) FROM orders WHERE o_custkey=c_custkey) > 1000*1000;

The query takes 40 seconds over cold cache

EXPLAIN: { "query_block": { "select_id": 1, "r_loops": 1, "r_total_time_ms": 39872, "table": { "table_name": "customer", "access_type": "index", "key": "i_c_nationkey", "key_length": "5", "used_key_parts": ["c_nationkey"], "r_loops": 1, "rows": 150303, "r_rows": 150000, "r_total_time_ms": 270.3, "filtered": 100, "r_filtered": 60.691, "attached_condition": "((subquery#2) > <cache>((1000 * 1000)))", "using_index": true }, "subqueries": [ { "query_block": { "select_id": 2, "r_loops": 150000, "r_total_time_ms": 39531, "table": { "table_name": "orders", "access_type": "ref", "possible_keys": ["i_o_custkey"], "key": "i_o_custkey", "key_length": "5", "used_key_parts": ["o_custkey"], "ref": ["dbt3sf1.customer.c_custkey"], "r_loops": 150000, "rows": 7, "r_rows": 10, "r_total_time_ms": 39208, "filtered": 100, "r_filtered": 100 } } } ] } }

ANALYZE shows that 39.2 seconds were spent in the subquery, which was executed 150K times (for every row of outer table).

1.1.2.2.3 ANALYZE Statement

Description

The ANALYZE statement is similar to the EXPLAIN statement. ANALYZE statement will invoke the optimizer, execute the statement, and then produce EXPLAIN output instead of the result set. The EXPLAIN output will be annotated with statistics from statement execution.

This lets one check how close the optimizer's estimates about the query plan are to the reality. ANALYZE produces an overview, while the ANALYZE FORMAT=JSON command provides a more detailed view of the query plan and the query execution.

The syntax is

ANALYZE explainable_statement;

where the statement is any statement for which one can run EXPLAIN.

Command Output

Consider an example:

ANALYZE SELECT * FROM tbl1 
WHERE key1 
  BETWEEN 10 AND 200 AND 
  col1 LIKE 'foo%'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: tbl1
         type: range
possible_keys: key1
          key: key1
      key_len: 5
          ref: NULL
         rows: 181
       r_rows: 181
     filtered: 100.00
   r_filtered: 10.50
        Extra: Using index condition; Using where

Compared to EXPLAIN, ANALYZE produces two extra columns:

  • r_rows is an observation-based counterpart of the rows column. It shows how many rows were actually read from the table.
  • r_filtered is an observation-based counterpart of the filtered column. It shows which fraction of rows was left after applying the WHERE condition.

Interpreting the Output

Joins

Let's consider a more complicated example.

ANALYZE SELECT *
FROM orders, customer 
WHERE
  customer.c_custkey=orders.o_custkey AND
  customer.c_acctbal < 0 AND
  orders.o_totalprice > 200*1000
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table    | type | possible_keys | key         | key_len | ref                | rows   | r_rows | filtered | r_filtered | Extra       |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
|  1 | SIMPLE      | customer | ALL  | PRIMARY,...   | NULL        | NULL    | NULL               | 149095 | 150000 |    18.08 |       9.13 | Using where |
|  1 | SIMPLE      | orders   | ref  | i_o_custkey   | i_o_custkey | 5       | customer.c_custkey |      7 |     10 |   100.00 |      30.03 | Using where |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+

Here, one can see that

  • For table customer, customer.rows=149095, customer.r_rows=150000. The estimate for number of rows we will read was fairly precise
  • customer.filtered=18.08, customer.r_filtered=9.13. The optimizer somewhat overestimated the number of records that will match selectivity of condition attached to `customer` table (in general, when you have a full scan and r_filtered is less than 15%, it's time to consider adding an appropriate index).
  • For table orders, orders.rows=7, orders.r_rows=10. This means that on average, there are 7 orders for a given c_custkey, but in our case there were 10, which is close to the expectation (when this number is consistently far from the expectation, it may be time to run ANALYZE TABLE, or even edit the table statistics manually to get better query plans).
  • orders.filtered=100, orders.r_filtered=30.03. The optimizer didn't have any way to estimate which fraction of records will be left after it checks the condition that is attached to table orders (it's orders.o_totalprice > 200*1000). So, it used 100%. In reality, it is 30%. 30% is typically not selective enough to warrant adding new indexes. For joins with many tables, it might be worth to collect and use column statistics for columns in question, this may help the optimizer to pick a better query plan.

Meaning of NULL in r_rows and r_filtered

Let's modify the previous example slightly

ANALYZE SELECT * 
FROM orders, customer 
WHERE
  customer.c_custkey=orders.o_custkey AND
  customer.c_acctbal < -0 AND 
  customer.c_comment LIKE '%foo%' AND
  orders.o_totalprice > 200*1000;
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table    | type | possible_keys | key         | key_len | ref                | rows   | r_rows | filtered | r_filtered | Extra       |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
|  1 | SIMPLE      | customer | ALL  | PRIMARY,...   | NULL        | NULL    | NULL               | 149095 | 150000 |    18.08 |       0.00 | Using where |
|  1 | SIMPLE      | orders   | ref  | i_o_custkey   | i_o_custkey | 5       | customer.c_custkey |      7 |   NULL |   100.00 |       NULL | Using where |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+

Here, one can see that orders.r_rows=NULL and orders.r_filtered=NULL. This means that table orders was not scanned even once. Indeed, we can also see customer.r_filtered=0.00. This shows that a part of WHERE attached to table `customer` was never satisfied (or, satisfied in less than 0.01% of cases).

ANALYZE FORMAT=JSON

ANALYZE FORMAT=JSON produces JSON output. It produces much more information than tabular ANALYZE.

Notes

  • ANALYZE UPDATE or ANALYZE DELETE will actually make updates/deletes (ANALYZE SELECT will perform the select operation and then discard the resultset).
  • PostgreSQL has a similar command, EXPLAIN ANALYZE.
  • The EXPLAIN in the slow query log feature allows MariaDB to have ANALYZE output of slow queries printed into the slow query log (see MDEV-6388).

See Also

1.1.2.2.4 EXPLAIN

Syntax

EXPLAIN tbl_name

Or

EXPLAIN [EXTENDED | PARTITIONS] 
  {SELECT select_options | UPDATE update_options | DELETE delete_options}

Description

The EXPLAIN statement can be used either as a synonym for DESCRIBE or as a way to obtain information about how MariaDB executes a SELECT, UPDATE or DELETE statement:

  • 'EXPLAIN tbl_name' is synonymous with 'DESCRIBE tbl_name' or 'SHOW COLUMNS FROM tbl_name'.
  • When you precede a SELECT, UPDATE or a DELETE statement with the keyword EXPLAIN, MariaDB displays information from the optimizer about the query execution plan. That is, MariaDB explains how it would process the SELECT, UPDATE or DELETE, including information about how tables are joined and in which order. EXPLAIN EXTENDED can be used to provide additional information.
  • EXPLAIN PARTITIONS is useful only when examining queries involving partitioned tables.
    For details, see Partition pruning and selection.
  • ANALYZE statement performs the query as well as producing EXPLAIN output, and provides actual as well as estimated statistics.
  • EXPLAIN output can be printed in the slow query log. See EXPLAIN in the Slow Query Log for details.

SHOW EXPLAIN shows the output of a running statement. In some cases, its output can be closer to reality than EXPLAIN.

The ANALYZE statement runs a statement and returns information about its execution plan. It also shows additional columns, to check how much the optimizer's estimation about filtering and found rows are close to reality.

There is an online EXPLAIN Analyzer that you can use to share EXPLAIN and EXPLAIN EXTENDED output with others.

EXPLAIN can acquire metadata locks in the same way that SELECT does, as it needs to know table metadata and, sometimes, data as well.

Columns in EXPLAIN ... SELECT

Column nameDescription
idSequence number that shows in which order tables are joined.
select_typeWhat kind of SELECT the table comes from.
tableAlias name of table. Materialized temporary tables for sub queries are named <subquery#>
typeHow rows are found from the table (join type).
possible_keyskeys in table that could be used to find rows in the table
keyThe name of the key that is used to retrieve rows. NULL is no key was used.
key_lenHow many bytes of the key that was used (shows if we are using only parts of the multi-column key).
refThe reference that is used as the key value.
rowsAn estimate of how many rows we will find in the table for each key lookup.
ExtraExtra information about this join.

Here are descriptions of the values for some of the more complex columns in EXPLAIN ... SELECT:

"Select_type" Column

The select_type column can have the following values:

ValueDescriptionComment
DEPENDENT SUBQUERYThe SUBQUERY is DEPENDENT.
DEPENDENT UNIONThe UNION is DEPENDENT.
DERIVEDThe SELECT is DERIVED from the PRIMARY.
MATERIALIZEDThe SUBQUERY is MATERIALIZED.Materialized tables will be populated at first access and will be accessed by the primary key (= one key lookup). Number of rows in EXPLAIN shows the cost of populating the table
PRIMARYThe SELECT is a PRIMARY one.
SIMPLEThe SELECT is a SIMPLE one.
SUBQUERYThe SELECT is a SUBQUERY of the PRIMARY.
UNCACHEABLE SUBQUERYThe SUBQUERY is UNCACHEABLE.
UNCACHEABLE UNIONThe UNION is UNCACHEABLE.
UNIONThe SELECT is a UNION of the PRIMARY.
UNION RESULTThe result of the UNION.
LATERAL DERIVEDThe SELECT uses a Lateral Derived optimization

"Type" Column

This column contains information on how the table is accessed.

ValueDescription
ALLA full table scan is done for the table (all rows are read). This is bad if the table is large and the table is joined against a previous table! This happens when the optimizer could not find any usable index to access rows.
constThere is only one possibly matching row in the table. The row is read before the optimization phase and all columns in the table are treated as constants.
eq_refA unique index is used to find the rows. This is the best possible plan to find the row.
fulltextA fulltext index is used to access the rows.
index_mergeA 'range' access is done for for several index and the found rows are merged. The key column shows which keys are used.
index_subqueryThis is similar as ref, but used for sub queries that are transformed to key lookups.
indexA full scan over the used index. Better than ALL but still bad if index is large and the table is joined against a previous table.
rangeThe table will be accessed with a key over one or more value ranges.
ref_or_nullLike 'ref' but in addition another search for the 'null' value is done if the first value was not found. This happens usually with sub queries.
refA non unique index or prefix of an unique index is used to find the rows. Good if the prefix doesn't match many rows.
systemThe table has 0 or 1 rows.
unique_subqueryThis is similar as eq_ref, but used for sub queries that are transformed to key lookups

"Extra" Column

This column consists of one or more of the following values, separated by ';'

Note that some of these values are detected after the optimization phase.

The optimization phase can do the following changes to the WHERE clause:

  • Add the expressions from the ON and USING clauses to the WHERE clause.
  • Constant propagation: If there is column=constant, replace all column instances with this constant.
  • Replace all columns from 'const' tables with their values.
  • Remove the used key columns from the WHERE (as this will be tested as part of the key lookup).
  • Remove impossible constant sub expressions. For example WHERE '(a=1 and a=2) OR b=1' becomes 'b=1'.
  • Replace columns with other columns that has identical values: Example: WHERE a=b and a=c may be treated as 'WHERE a=b and a=c and b=c'.
  • Add extra conditions to detect impossible row conditions earlier. This happens mainly with OUTER JOIN where we in some cases add detection of NULL values in the WHERE (Part of 'Not exists' optimization). This can cause an unexpected 'Using where' in the Extra column.
  • For each table level we remove expressions that have already been tested when we read the previous row. Example: When joining tables t1 with t2 using the following WHERE 't1.a=1 and t1.a=t2.b', we don't have to test 't1.a=1' when checking rows in t2 as we already know that this expression is true.
ValueDescription
const row not foundThe table was a system table (a table with should exactly one row), but no row was found.
DistinctIf distinct optimization (remove duplicates) was used. This is marked only for the last table in the SELECT.
Full scan on NULL keyThe table is a part of the sub query and if the value that is used to match the sub query will be NULL, we will do a full table scan.
Impossible HAVINGThe used HAVING clause is always false so the SELECT will return no rows.
Impossible WHERE noticed after reading const tables.The used WHERE clause is always false so the SELECT will return no rows. This case was detected after we had read all 'const' tables and used the column values as constant in the WHERE clause. For example: WHERE const_column=5 and const_column had a value of 4.
Impossible WHEREThe used WHERE clause is always false so the SELECT will return no rows. For example: WHERE 1=2
No matching min/max rowDuring early optimization of MIN()/MAX() values it was detected that no row could match the WHERE clause. The MIN()/MAX() function will return NULL.
no matching row in const tableThe table was a const table (a table with only one possible matching row), but no row was found.
No tables usedThe SELECT was a sub query that did not use any tables. For example a there was no FROM clause or a FROM DUAL clause.
Not existsStop searching after more row if we find one single matching row. This optimization is used with LEFT JOIN where one is explicitly searching for rows that doesn't exists in the LEFT JOIN TABLE. Example: SELECT * FROM t1 LEFT JOIN t2 on (...) WHERE t2.not_null_column IS NULL. As t2.not_null_column can only be NULL if there was no matching row for on condition, we can stop searching if we find a single matching row.
Open_frm_onlyFor information_schema tables. Only the frm (table definition file was opened) was opened for each matching row.
Open_full_tableFor information_schema tables. A full table open for each matching row is done to retrieve the requested information. (Slow)
Open_trigger_onlyFor information_schema tables. Only the trigger file definition was opened for each matching row.
Range checked for each record (index map: ...)This only happens when there was no good default index to use but there may some index that could be used when we can treat all columns from previous table as constants. For each row combination the optimizer will decide which index to use (if any) to fetch a row from this table. This is not fast, but faster than a full table scan that is the only other choice. The index map is a bitmask that shows which index are considered for each row condition.
Scanned 0/1/all databasesFor information_schema tables. Shows how many times we had to do a directory scan.
Select tables optimized awayAll tables in the join was optimized away. This happens when we are only using COUNT(*), MIN() and MAX() functions in the SELECT and we where able to replace all of these with constants.
Skip_open_tableFor information_schema tables. The queried table didn't need to be opened.
unique row not foundThe table was detected to be a const table (a table with only one possible matching row) during the early optimization phase, but no row was found.
Using filesortFilesort is needed to resolve the query. This means an extra phase where we first collect all columns to sort, sort them with a disk based merge sort and then use the sorted set to retrieve the rows in sorted order. If the column set is small, we store all the columns in the sort file to not have to go to the database to retrieve them again.
Using indexOnly the index is used to retrieve the needed information from the table. There is no need to perform an extra seek to retrieve the actual record.
Using index conditionLike 'Using where' but the where condition is pushed down to the table engine for internal optimization at the index level.
Using index condition(BKA)Like 'Using index condition' but in addition we use batch key access to retrieve rows.
Using index for group-byThe index is being used to resolve a GROUP BY or DISTINCT query. The rows are not read. This is very efficient if the table has a lot of identical index entries as duplicates are quickly jumped over.
Using intersect(...)For index_merge joins. Shows which index are part of the intersect.
Using join bufferWe store previous row combinations in a row buffer to be able to match each row against all of the rows combinations in the join buffer at one go.
Using sort_union(...)For index_merge joins. Shows which index are part of the union.
Using temporaryA temporary table is created to hold the result. This typically happens if you are using GROUP BY, DISTINCT or ORDER BY.
Using whereA WHERE expression (in additional to the possible key lookup) is used to check if the row should be accepted. If you don't have 'Using where' together with a join type of ALL, you are probably doing something wrong!
Using where with pushed conditionLike 'Using where' but the where condition is pushed down to the table engine for internal optimization at the row level.
Using bufferThe UPDATE statement will first buffer the rows, and then run the updates, rather than do updates on the fly. See Using Buffer UPDATE Algorithm for a detailed explanation.

EXPLAIN EXTENDED

The EXTENDED keyword adds another column, filtered, to the output. This is a percentage estimate of the table rows that will be filtered by the condition.

An EXPLAIN EXTENDED will always throw a warning, as it adds extra Message information to a subsequent SHOW WARNINGS statement. This includes what the SELECT query would look like after optimizing and rewriting rules are applied and how the optimizer qualifies columns and tables.

Examples

As synonym for DESCRIBE or SHOW COLUMNS FROM:

DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | YES  |     | NULL    |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+

A simple set of examples to see how EXPLAIN can identify poor index usage:

CREATE TABLE IF NOT EXISTS `employees_example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(30) NOT NULL,
  `last_name` varchar(40) NOT NULL,
  `position` varchar(25) NOT NULL,
  `home_address` varchar(50) NOT NULL,
  `home_phone` varchar(12) NOT NULL,
  `employee_code` varchar(25) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `employee_code` (`employee_code`),
  KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;

INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`)
  VALUES
  ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'),
  ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'),
  ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'),
  ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'),
  ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'),
  ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1');

SHOW INDEXES FROM employees_example;
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table             | Non_unique | Key_name      | Seq_in_index | Column_name   | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| employees_example |          0 | PRIMARY       |            1 | id            | A         |           7 |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          0 | employee_code |            1 | employee_code | A         |           7 |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          1 | first_name    |            1 | first_name    | A         |        NULL |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          1 | first_name    |            2 | last_name     | A         |        NULL |     NULL | NULL   |      | BTREE      |         |               |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

SELECT on a primary key:

EXPLAIN SELECT * FROM employees_example WHERE id=1;
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
| id   | select_type | table             | type  | possible_keys | key     | key_len | ref   | rows | Extra |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
|    1 | SIMPLE      | employees_example | const | PRIMARY       | PRIMARY | 4       | const |    1 |       |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+

The type is const, which means that only one possible result could be returned. Now, returning the same record but searching by their phone number:

EXPLAIN SELECT * FROM employees_example WHERE home_phone='326-555-3492';
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
| id   | select_type | table             | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
|    1 | SIMPLE      | employees_example | ALL  | NULL          | NULL | NULL    | NULL |    6 | Using where |
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+

Here, the type is All, which means no index could be used. Looking at the rows count, a full table scan (all six rows) had to be performed in order to retrieve the record. If it's a requirement to search by phone number, an index will have to be created.

SHOW EXPLAIN example:

SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
|    1 | SIMPLE      | tbl   | index | NULL          | a    | 5       | NULL | 1000107 | Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)

Example of ref_or_null Optimization

SELECT * FROM table_name
  WHERE key_column=expr OR key_column IS NULL;

ref_or_null is something that often happens when you use subqueries with NOT IN as then one has to do an extra check for NULL values if the first value didn't have a matching row.

See Also

1.1.2.2.5 EXPLAIN ANALYZE

The syntax for the EXPLAIN ANALYZE feature was changed to ANALYZE statement, available since MariaDB 10.1.0. See ANALYZE statement.

1.1.2.2.6 EXPLAIN FORMAT=JSON

MariaDB starting with 10.1.2

Starting from version 10.1.2, MariaDB supports the EXPLAIN FORMAT=JSON syntax.

Synopsis

EXPLAIN FORMAT=JSON is a variant of EXPLAIN command that produces output in JSON form. The output always has one row which has only one column titled "JSON". The contents are a JSON representation of the query plan, formatted for readability:

EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE col1=1\G
*************************** 1. row ***************************
EXPLAIN: {
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t1",
      "access_type": "ALL",
      "rows": 1000,
      "filtered": 100,
      "attached_condition": "(t1.col1 = 1)"
    }
  }
}

Output is different from MySQL

The output of MariaDB's EXPLAIN FORMAT=JSON is different from EXPLAIN FORMAT=JSON in MySQL.The reasons for that are:

  • MySQL's output has deficiencies. Some are listed here: EXPLAIN FORMAT=JSON in MySQL
  • The output of MySQL's EXPLAIN FORMAT=JSON is not defined. Even MySQL Workbench has trouble parsing it (see this blog post).
  • MariaDB has query optimizations that MySQL does not have. Ergo, MariaDB generates query plans that MySQL does not generate.

A (as yet incomplete) list of how MariaDB's output is different from MySQL can be found here: EXPLAIN FORMAT=JSON differences from MySQL.

Output format

TODO: MariaDB's output format description.

See also

  • ANALYZE FORMAT=JSON produces output like EXPLAIN FORMAT=JSON, but amended with the data from query execution.

1.1.2.2.7 SHOW EXPLAIN

Syntax

SHOW EXPLAIN FOR <thread_id>;

Description

The SHOW EXPLAIN command allows one to get an EXPLAIN (that is, a description of a query plan) of a query running in a certain thread.

SHOW EXPLAIN FOR <thread_id>;

will produce an EXPLAIN output for the query that thread number thread_id is running. The thread id can be obtained with SHOW PROCESSLIST.

SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
|    1 | SIMPLE      | tbl   | index | NULL          | a    | 5       | NULL | 1000107 | Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)

The output is always accompanied with a warning which shows the query the target thread is running (this shows what the EXPLAIN is for):

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1003 | select sum(a) from tbl |
+-------+------+------------------------+
1 row in set (0.00 sec)

Possible Errors

The output can be only produced if the target thread is currently running a query, which has a ready query plan. If this is not the case, the output will be:

SHOW EXPLAIN FOR 2;
ERROR 1932 (HY000): Target is not running an EXPLAINable command

You will get this error when:

  • the target thread is not running a command for which one can run EXPLAIN
  • the target thread is running a command for which one can run EXPLAIN, but
    • there is no query plan yet (for example, tables are open and locks are acquired before the query plan is produced)

Differences Between SHOW EXPLAIN and EXPLAIN Outputs

Background

In MySQL, EXPLAIN execution takes a slightly different route from the way the real query (typically the SELECT) is optimized. This is unfortunate, and has caused a number of bugs in EXPLAIN. (For example, see MDEV-326, MDEV-410, and lp:1013343. lp:992942 is not directly about EXPLAIN, but it also would not have existed if MySQL didn't try to delete parts of a query plan in the middle of the query)

SHOW EXPLAIN examines a running SELECT, and hence its output may be slightly different from what EXPLAIN SELECT would produce. We did our best to make sure that either the difference is negligible, or SHOW EXPLAIN's output is closer to reality than EXPLAIN's output.

List of Recorded Differences

  • SHOW EXPLAIN may have Extra='no matching row in const table', where EXPLAIN would produce Extra='Impossible WHERE ...'
  • For queries with subqueries, SHOW EXPLAIN may print select_type==PRIMARY where regular EXPLAIN used to print select_type==SIMPLE, or vice versa.

Required Permissions

Running SHOW EXPLAIN requires the same permissions as running SHOW PROCESSLIST would.

See Also

1.1.2.2.8 Using Buffer UPDATE Algorithm

This article explains the UPDATE statement's Using Buffer algorithm.

Take the following table and query:

NameSalary
Babatunde1000
Jolana1050
Pankaja1300
UPDATE employees SET salary = salary+100 WHERE salary < 2000;

Suppose the employees table has an index on the salary column, and the optimizer decides to use a range scan on that index.

The optimizer starts a range scan on the salary index. We find the first record Babatunde, 1000. If we do an on-the-fly update, we immediately instruct the storage engine to change this record to be Babatunde, 1000+100=1100.

Then we proceed to search for the next record, and find Jolana, 1050. We instruct the storage engine to update it to be Jolana, 1050+100=1150.

Then we proceed to search for the next record ... and what happens next depends on the storage engine. In some storage engines, data changes are visible immediately, so we will find find the Babatunde, 1100 record that we wrote at the first step, modifying it again, giving Babatunde an undeserved raise. Then we will see Babatunde again and again, looping continually.

In order to prevent such situations, the optimizer checks whether the UPDATE statement is going to change key values for the keys it is using. In that case, it will use a different algorithm:

  1. Scan everyone with "salary<2000", remembering the rowids of the rows in a buffer.
  2. Read the buffer and apply the updates.

This way, each row will be updated only once.

The Using buffer EXPLAIN output indicates that the buffer as described above will be used. The algorithm has always been in use, but has only been made visible in the EXPLAIN output since MariaDB 10.0.5.

1.1.2.3 BACKUP Commands

1.1.2.3.1 BACKUP STAGE

MariaDB starting with 10.4.1

The BACKUP STAGE commands were introduced in MariaDB 10.4.1.

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool.

Syntax

BACKUP STAGE [START | FLUSH | BLOCK_DDL | BLOCK_COMMIT | END ]

In the following text, a transactional table means InnoDB or "InnoDB-like engine with redo log that can lock redo purges and can be copied without locks by an outside process".

Goals with BACKUP STAGE Commands

  • To be able to do a majority of the backup with the minimum possible server locks. Especially for transactional tables (InnoDB, MyRocks etc) there is only need for a very short block of new commits while copying statistics and log tables.
  • DDL are only needed to be blocked for a very short duration of the backup while mariabackup is copying the tables affected by DDL during the initial part of the backup.
  • Most non transactional tables (those that are not in use) will be copied during BACKUP STAGE START. The exceptions are system statistic and log tables that are not blocked during the backup until BLOCK_COMMIT.
  • Should work efficiently with backup tools that use disk snapshots.
  • Should work as efficiently as possible for all table types that store data on the local disks.
  • As little copying as possible under higher level stages/locks. For example, .frm (dictionary) and .trn (trigger) files should be copying while copying the table data.

BACKUP STAGE Commands

BACKUP STAGE START

The START stage is designed for the following tasks:

  • Blocks purge of redo files for storage engines that needs this (Aria)
  • Start logging of DDL commands into 'datadir'/ddl.log. This may take a short time as the command has to wait until there are no active DDL commands.

BACKUP STAGE FLUSH

The FLUSH stage is designed for the following tasks:

  • FLUSH all changes for inactive non-transactional tables, except for statistics and log tables.
  • Close all tables that are not in use, to ensure they are marked as closed for the backup.
  • BLOCK all new write locks for all non transactional tables (except statistics and log tables). The command will not wait for tables that are in use by read-only transactions.

DDLs don't have to be blocked at this stage as they can't cause the table to be in an inconsistent state. This is true also for non-transactional tables.

BACKUP STAGE BLOCK_DDL

The BLOCK_DDL stage is designed for the following tasks:

BACKUP STAGE BLOCK_COMMIT

The BLOCK_COMMIT stage is designed for the following tasks:

  • Lock the binary log and commit/rollback to ensure that no changes are committed to any tables. If there are active commits or data to be copied to the binary log this will be allowed to finish. Active transactions will not affect BLOCK_COMMIT.
  • This doesn't lock temporary tables that are not used by replication. However these will be blocked when it's time to write to the binary log.
  • Lock system log tables and statistics tables, flush them and mark them closed.

When the BLOCK_COMMIT's stages return, this is the 'backup time'. Everything committed will be in the backup and everything not committed will roll back.

Transactional engines will continue to do changes to the redo log during the BLOCK COMMIT stage, but this is not important as all of these will roll back later as the changes will not be committed.

BACKUP STAGE END

The END stage is designed for the following tasks:

  • End DDL logging
  • Free resources

Using BACKUP STAGE Commands with Backup Tools

Using BACKUP STAGE Commands with Mariabackup

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. How Mariabackup uses these commands depends on whether you are using the version that is bundled with MariaDB Community Server or the version that is bundled with MariaDB Enterprise Server. See Mariabackup and BACKUP STAGE Commands for some examples on how Mariabackup uses these commands.

If you would like to use a version of Mariabackup that uses the BACKUP STAGE commands in an efficient way, then one option is to use MariaDB Enterprise Backup that is bundled with MariaDB Enterprise Server.

Using BACKUP STAGE Commands with Storage Snapshots

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. These commands could even be used by tools that perform backups by taking a snapshot of a file system, SAN, or some other kind of storage device. See Storage Snapshots and BACKUP STAGE Commands for some examples on how to use each BACKUP STAGE command in an efficient way.

Privileges

BACKUP STAGE requires the RELOAD privilege.

Notes

  • Only one connection can run BACKUP STAGE START. If a second connection tries, it will wait until the first one has executed BACKUP STAGE END.
  • If the user skips a BACKUP STAGE, then all intermediate backup stages will automatically be run. This will allow us to add new stages within the BACKUP STAGE hierarchy in the future with even more precise locks without causing problems for tools using an earlier version of the BACKUP STAGE implementation.
  • One can use the max_statement_time or lock_wait_timeout system variables to ensure that a BACKUP STAGE command doesn't block the server too long.
  • DDL logging will only be available in MariaDB Enterprise Server 10.2 and later.

See Also

  • BACKUP LOCK Locking a table from DDL's.
  • MDEV-5336. Implement BACKUP STAGE for safe external backups.

1.1.2.3.2 BACKUP LOCK

MariaDB starting with 10.4.2

The BACKUP LOCK command was introduced in MariaDB 10.4.2.

BACKUP LOCK blocks a table from DDL statements. This is mainly intended to be used by tools like mariabackup that need to ensure there are no DDLs on a table while the table files are opened. For example, for an Aria table that stores data in 3 files with extensions .frm, .MAI and .MAD. Normal read/write operations can continue as normal.

Syntax

To lock a table:

BACKUP LOCK table_name

To unlock a table:

BACKUP UNLOCK

Usage in a Backup Tool

BACKUP LOCK [database.]table_name;
 - Open all files related to a table (for example, t.frm, t.MAI and t.MYD)
BACKUP UNLOCK;
- Copy data
- Close files

This ensures that all files are from the same generation, that is created at the same time by the MariaDB server. This works, because the open files will point to the original table files which will not be affected if there is any ALTER TABLE while copying the files.

Privileges

BACKUP LOCK requires the RELOAD privilege.

Notes

  • The idea is that the BACKUP LOCK should be held for as short a time as possible by the backup tool. The time to take an uncontested lock is very short! One can easily do 50,000 locks/unlocks per second on low end hardware.
  • One should use different connections for BACKUP STAGE commands and BACKUP LOCK.

Implementation

  • Internally, BACKUP LOCK is implemented by taking an MDLSHARED_HIGH_PRIO MDL lock on the table object, which protects the table from any DDL operations.

See Also

1.1.2.3.3 Mariabackup and BACKUP STAGE Commands

MariaDB starting with 10.4.1

The BACKUP STAGE commands were introduced in MariaDB 10.4.1.

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. How Mariabackup uses these commands depends on whether you are using the version that is bundled with MariaDB Community Server or the version that is bundled with MariaDB Enterprise Server.

Mariabackup and BACKUP STAGE Commands in MariaDB Community Server

MariaDB starting with 10.4.1

In MariaDB Community Server, Mariabackup first supported BACKUP STAGE commands in MariaDB 10.4.1.

In MariaDB 10.3 and before, the BACKUP STAGE commands are not supported, so Mariabackup executes the FLUSH TABLES WITH READ LOCK command to lock the database. When the backup is complete, it executes the UNLOCK TABLES command to unlock the database.

In MariaDB 10.4 and later, the BACKUP STAGE commands are supported. However, the version of Mariabackup that is bundled with MariaDB Community Server does not yet use the BACKUP STAGE commands in the most efficient way. Mariabackup simply executes the following BACKUP STAGE commands to lock the database:

BACKUP STAGE START;
BACKUP STAGE BLOCK_COMMIT;

When the backup is complete, it executes the following BACKUP STAGE command to unlock the database:

BACKUP STAGE END;

If you would like to use a version of Mariabackup that uses the BACKUP STAGE commands in the most efficient way, then your best option is to use MariaDB Enterprise Backup that is bundled with MariaDB Enterprise Server.

Tasks Performed Prior to BACKUP STAGE in MariaDB Community Server

  • Copy some transactional tables.
    • InnoDB (i.e. ibdataN and file extensions .ibd and .isl)
  • Copy the tail of some transaction logs.

BACKUP STAGE START in MariaDB Community Server

Mariabackup from MariaDB Community Server does not currently perform any tasks in the START stage.

BACKUP STAGE FLUSH in MariaDB Community Server

Mariabackup from MariaDB Community Server does not currently perform any tasks in the FLUSH stage.

BACKUP STAGE BLOCK_DDL in MariaDB Community Server

Mariabackup from MariaDB Community Server does not currently perform any tasks in the BLOCK_DDL stage.

BACKUP STAGE BLOCK_COMMIT in MariaDB Community Server

Mariabackup from MariaDB Community Server performs the following tasks in the BLOCK_COMMIT stage:

BACKUP STAGE END in MariaDB Community Server

Mariabackup from MariaDB Community Server performs the following tasks in the END stage:

  • Copy the MyRocks checkpoint into the backup.

Mariabackup and BACKUP STAGE Commands in MariaDB Enterprise Server

The following sections describe how the MariaDB Enterprise Backup version of Mariabackup that is bundled with MariaDB Enterprise Server uses each BACKUP STAGE command in an efficient way.

BACKUP STAGE START in MariaDB Enterprise Server

Mariabackup from MariaDB Enterprise Server performs the following tasks in the START stage:

  • Copy all transactional tables.
    • InnoDB (i.e. ibdataN and file extensions .ibd and .isl)
    • Aria (i.e. aria_log_control and file extensions .MAD and .MAI)
  • Copy the tail of all transaction logs.
    • The tail of the InnoDB redo log (i.e. ib_logfileN files) will be copied for InnoDB tables.
    • The tail of the Aria redo log (i.e. aria_log.N files) will be copied for Aria tables.

BACKUP STAGE FLUSH in MariaDB Enterprise Server

Mariabackup from MariaDB Enterprise Server performs the following tasks in the FLUSH stage:

  • Copy all non-transactional tables that are not in use. This list of used tables is found with SHOW OPEN TABLES.
    • MyISAM (i.e. file extensions .MYD and .MYI)
    • MERGE (i.e. file extensions .MRG)
    • ARCHIVE (i.e. file extensions .ARM and .ARZ)
    • CSV (i.e. file extensions .CSM and .CSV)
  • Copy the tail of all transaction logs.
    • The tail of the InnoDB redo log (i.e. ib_logfileN files) will be copied for InnoDB tables.
    • The tail of the Aria redo log (i.e. aria_log.N files) will be copied for Aria tables.

BACKUP STAGE BLOCK_DDL in MariaDB Enterprise Server

Mariabackup from MariaDB Enterprise Server performs the following tasks in the BLOCK_DDL stage:

  • Copy other files.
    • i.e. file extensions .frm, .isl, .TRG, .TRN, .opt, .par
  • Copy the non-transactional tables that were in use during BACKUP STAGE FLUSH.
    • MyISAM (i.e. file extensions .MYD and .MYI)
    • MERGE (i.e. file extensions .MRG)
    • ARCHIVE (i.e. file extensions .ARM and .ARZ)
    • CSV (i.e. file extensions .CSM and .CSV)
  • Check ddl.log for DDL executed before the BLOCK DDL stage.
    • The file names of newly created tables can be read from ddl.log.
    • The file names of dropped tables can also be read from ddl.log.
    • The file names of renamed tables can also be read from ddl.log, so the files can be renamed instead of re-copying them.
  • Copy changes to system log tables.
  • Copy the tail of all transaction logs.
    • The tail of the InnoDB redo log (i.e. ib_logfileN files) will be copied for InnoDB tables.
    • The tail of the Aria redo log (i.e. aria_log.N files) will be copied for Aria tables.

BACKUP STAGE BLOCK_COMMIT in MariaDB Enterprise Server

Mariabackup from MariaDB Enterprise Server performs the following tasks in the BLOCK_COMMIT stage:

BACKUP STAGE END in MariaDB Enterprise Server

Mariabackup from MariaDB Enterprise Server performs the following tasks in the END stage:

  • Copy the MyRocks checkpoint into the backup.

1.1.2.3.4 Storage Snapshots and BACKUP STAGE Commands

MariaDB starting with 10.4.1

The BACKUP STAGE commands were introduced in MariaDB 10.4.1.

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. These commands could even be used by tools that perform backups by taking a snapshot of a file system, SAN, or some other kind of storage device.

Generic Backup Process with Storage Snapshots

A tool that backs up MariaDB by taking a snapshot of a file system, SAN, or some other kind of storage device could use each BACKUP STAGE command in the following way:

  • First, execute the following:
BACKUP STAGE START
BACKUP STAGE BLOCK_COMMIT
  • Then, take the snapshot.
  • Then, execute the following:
BACKUP STAGE END

The above ensures that all non-transactional tables are properly flushed to disk before the snapshot is done. Using BACKUP STAGE commands is also more efficient than using the FLUSH TABLES WITH READ LOCK command as the above set of commands will not block or be blocked by write operations to transactional tables.

Note that when the backup is completed, one should delete all files with the "#storage-snapshots-and-backup-stage-commandssql" prefix, as these are files used by concurrent running ALTER TABLE. Note that InnoDB will on server restart automatically delete any tables with the "#storage-snapshots-and-backup-stage-commandssql" prefix.

1.1.2.4 FLUSH Commands

1.1.2.4.1 FLUSH

Syntax

FLUSH [NO_WRITE_TO_BINLOG | LOCAL]
    flush_option [, flush_option] ...

or when flushing tables:

FLUSH [NO_WRITE_TO_BINLOG | LOCAL] TABLES [table_list]  [table_flush_option]

where table_list is a list of tables separated by , (comma).

Description

The FLUSH statement clears or reloads various internal caches used by MariaDB. To execute FLUSH, you must have the RELOAD privilege. See GRANT.

The RESET statement is similar to FLUSH. See RESET.

You cannot issue a FLUSH statement from within a stored function or a trigger. Doing so within a stored procedure is permitted, as long as it is not called by a stored function or trigger. See Stored Routine Limitations, Stored Function Limitations and Trigger Limitations.

If a listed table is a view, an error like the following will be produced:

ERROR 1347 (HY000): 'test.v' is not BASE TABLE

By default, FLUSH statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

The different flush options are:

OptionDescription
CHANGED_PAGE_BITMAPSInternal command used for backup purposes. See the Information Schema CHANGED_PAGE_BITMAPS Table.
CLIENT_STATISTICSReset client statistics (see SHOW CLIENT_STATISTICS).
DES_KEY_FILEReloads the DES key file (Specified with the --des-key-file startup option).
HOSTSFlush the hostname cache (used for converting ip to host names and for unblocking blocked hosts. See max_connect_errors)
INDEX_STATISTICSReset index statistics (see SHOW INDEX_STATISTICS).
[ERROR | ENGINE | GENERAL | SLOW | BINARY | RELAY] LOGSClose and reopen the specified log type, or all log types if none are specified. FLUSH RELAY LOGS [connection-name] can be used to flush the relay logs for a specific connection. Only one connection can be specified per FLUSH command. See Multi-source replication. FLUSH ENGINE LOGS will delete all unneeded Aria redo logs. Since MariaDB 10.1.30 and MariaDB 10.2.11, FLUSH BINARY LOGS DELETE_DOMAIN_ID=(list-of-domains) can be used to discard obsolete GTID domains from the server's binary log state. In order for this to be successful, no event group from the listed GTID domains can be present in existing binary log files. If some still exist, then they must be purged prior to executing this command. If the command completes successfully, then it also rotates the binary log.
MASTERDeprecated option, use RESET MASTER instead.
PRIVILEGESReload all privileges from the privilege tables in the mysql database. If the server is started with --skip-grant-table option, this will activate the privilege tables again.
QUERY CACHEDefragment the query cache to better utilize its memory. If you want to reset the query cache, you can do it with RESET QUERY CACHE.
QUERY_RESPONSE_TIMESee the QUERY_RESPONSE_TIME plugin.
SLAVEDeprecated option, use RESET REPLICA or RESET SLAVE instead.
SSLUsed to dynamically reinitialize the server's TLS context by reloading the files defined by several TLS system variables. See FLUSH SSL for more information. This command was first added in MariaDB 10.4.1.
STATUSResets all server status variables that can be reset to 0. Not all global status variables support this, so not all global values are reset. See FLUSH STATUS for more information.
TABLEClose tables given as options or all open tables if no table list was used. From MariaDB 10.4.1, using without any table list will only close tables not in use, and tables not locked by the FLUSH TABLES connection. If there are no locked tables, FLUSH TABLES will be instant and will not cause any waits, as it no longer waits for tables in use. When a table list is provided, from MariaDB 10.4.1, the server will wait for the end of any transactions that are using the tables. Previously, FLUSH TABLES only waited for the statements to complete.
TABLESSame as FLUSH TABLE.
TABLES ... FOR EXPORTFor InnoDB tables, flushes table changes to disk to permit binary table copies while the server is running. Introduced in MariaDB 10.0.8. See FLUSH TABLES ... FOR EXPORT for more.
TABLES WITH READ LOCKCloses all open tables. New tables are only allowed to be opened with read locks until an UNLOCK TABLES is given.
TABLES WITH READ LOCK AND DISABLE CHECKPOINTAs TABLES WITH READ LOCK but also disable all checkpoint writes by transactional table engines. This is useful when doing a disk snapshot of all tables.
TABLE_STATISTICSReset table statistics (see SHOW TABLE_STATISTICS).
USER_RESOURCESResets all per hour user resources. This enables clients that have exhausted their resources to connect again.
USER_STATISTICSReset user statistics (see SHOW USER_STATISTICS).

You can also use the mysqladmin client to flush things. Use mysqladmin --help to examine what flush commands it supports.

FLUSH STATUS

Server status variables can be reset by executing the following:

FLUSH STATUS;

Compatibility with MySQL

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after the FLUSH command.

For example, one can now use:

FLUSH RELAY LOGS 'connection_name';
FLUSH RELAY LOGS FOR CHANNEL 'connection_name';

Global Status Variables that Support FLUSH STATUS

Not all global status variables support being reset by FLUSH STATUS. Currently, the following status variables are reset by FLUSH STATUS:

The different usage of FLUSH TABLES

The purpose of FLUSH TABLES

The purpose of FLUSH TABLES is to clean up the open table cache and table definition cache from not in use tables. This frees up memory and file descriptors. Normally this is not needed as the caches works on a FIFO bases, but can be useful if the server seams to use up to much memory for some reason.

The purpose of FLUSH TABLES WITH READ LOCK

FLUSH TABLES WITH READ LOCK is useful if you want to take a backup of some tables. When FLUSH TABLES WITH READ LOCK returns, all write access to tables are blocked and all tables are marked as 'properly closed' on disk. The tables can still be used for read operations.

The purpose of FLUSH TABLES table_list

FLUSH TABLES table_list is useful if you want to copy a table object/files to or from the server. This command puts a lock that stops new users of the table and will wait until everyone has stopped using the table. The table is then removed from the table definition and table cache.

Note that it's up to the user to ensure that no one is accessing the table between FLUSH TABLES and the table is copied to or from the server. This can be secured by using LOCK TABLES.

If there are any tables locked by the connection that is using FLUSH TABLES all the locked tables will be closed as part of the flush and reopened and relocked before FLUSH TABLES returns. This allows one to copy the table after FLUSH TABLES returns without having any writes on the table. For now this works works with most tables, except InnoDB as InnoDB may do background purges on the table even while it's write locked.

The purpose of FLUSH TABLES table_list WITH READ LOCK

FLUSH TABLES table_list WITH READ LOCK should work as FLUSH TABLES WITH READ LOCK, but only those tables that are listed will be properly closed. However in practice this works exactly like FLUSH TABLES WITH READ LOCK as the FLUSH command has anyway to wait for all WRITE operations to end because we are depending on a global read lock for this code. In the future we should consider fixing this to instead use meta data locks.

Implementation of FLUSH TABLES commands in MariaDB 10.4.8 and above

Implementation of FLUSH TABLES

  • Free memory and file descriptors not in use

Implementation of FLUSH TABLES WITH READ LOCK

  • Lock all tables read only for simple old style backup.
  • All background writes are suspended and tables are marked as closed.
  • No statement requiring table changes are allowed for any user until UNLOCK TABLES.

Instead of using FLUSH TABLE WITH READ LOCK one should in most cases instead use BACKUP STAGE BLOCK_COMMIT.

Implementation of FLUSH TABLES table_list

  • Free memory and file descriptors for tables not in use from table list.
  • Lock given tables as read only.
  • Wait until all translations has ended that uses any of the given tables.
  • Wait until all background writes are suspended and tables are marked as closed.

Implementation of FLUSH TABLES table_list FOR EXPORT

  • Free memory and file descriptors for tables not in use from table list
  • Lock given tables as read.
  • Wait until all background writes are suspended and tables are marked as closed.
  • Check that all tables supports FOR EXPORT
  • No changes to these tables allowed until UNLOCK TABLES

This is basically the same behavior as in old MariaDB version if one first lock the tables, then do FLUSH TABLES. The tables will be copyable until UNLOCK TABLES.

FLUSH SSL

MariaDB starting with 10.4

The FLUSH SSL command was first added in MariaDB 10.4.

In MariaDB 10.4 and later, the FLUSH SSL command can be used to dynamically reinitialize the server's TLS context. This is most useful if you need to replace a certificate that is about to expire without restarting the server.

This operation is performed by reloading the files defined by the following TLS system variables:

These TLS system variables are not dynamic, so their values can not be changed without restarting the server.

If you want to dynamically reinitialize the server's TLS context, then you need to change the certificate and key files at the relevant paths defined by these TLS system variables, without actually changing the values of the variables. See MDEV-19341 for more information.

Reducing Memory Usage

To flush some of the global caches that take up memory, you could execute the following command:

FLUSH LOCAL HOSTS,
   QUERY CACHE, 
   TABLE_STATISTICS, 
   INDEX_STATISTICS, 
   USER_STATISTICS;

1.1.2.4.2 FLUSH QUERY CACHE

Description

You can defragment the query cache to better utilize its memory with the FLUSH QUERY CACHE statement. The statement does not remove any queries from the cache.

The RESET QUERY CACHE statement removes all query results from the query cache. The FLUSH TABLES statement also does this.

1.1.2.4.3 FLUSH TABLES FOR EXPORT

Syntax

FLUSH TABLES table_name [, table_name] FOR EXPORT

Description

FLUSH TABLES ... FOR EXPORT flushes changes to the specified tables to disk so that binary copies can be made while the server is still running. This works for Archive, Aria, CSV, InnoDB, MyISAM, MERGE, and XtraDB tables.

The table is read locked until one has issued UNLOCK TABLES.

If a storage engine does not support FLUSH TABLES FOR EXPORT, a 1031 error (SQLSTATE 'HY000') is produced.

If FLUSH TABLES ... FOR EXPORT is in effect in the session, the following statements will produce an error if attempted:

  • FLUSH TABLES WITH READ LOCK
  • FLUSH TABLES ... WITH READ LOCK
  • FLUSH TABLES ... FOR EXPORT
  • Any statement trying to update any table

If any of the following statements is in effect in the session, attempting FLUSH TABLES ... FOR EXPORT will produce an error.

  • FLUSH TABLES ... WITH READ LOCK
  • FLUSH TABLES ... FOR EXPORT
  • LOCK TABLES ... READ
  • LOCK TABLES ... WRITE

FLUSH FOR EXPORT is not written to the binary log.

This statement requires the RELOAD and the LOCK TABLES privileges.

If one of the specified tables cannot be locked, none of the tables will be locked.

If a table does not exist, an error like the following will be produced:

ERROR 1146 (42S02): Table 'test.xxx' doesn't exist

If a table is a view, an error like the following will be produced:

ERROR 1347 (HY000): 'test.v' is not BASE TABLE

Example

FLUSH TABLES test.t1 FOR EXPORT;
#  Copy files related to the table (see below)
UNLOCK TABLES;

For a full description, please see copying MariaDB tables.

See Also

1.1.2.5 Replication Commands

1.1.2.5.1 CHANGE MASTER TO

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

CHANGE MASTER ['connection_name'] TO master_def [, master_def] ... [FOR CHANNEL 'channel_name']

master_def:
    MASTER_BIND = 'interface_name'
  | MASTER_HOST = 'host_name'
  | MASTER_USER = 'user_name'
  | MASTER_PASSWORD = 'password'
  | MASTER_PORT = port_num
  | MASTER_CONNECT_RETRY = interval
  | MASTER_HEARTBEAT_PERIOD = interval
  | MASTER_LOG_FILE = 'master_log_name'
  | MASTER_LOG_POS = master_log_pos
  | RELAY_LOG_FILE = 'relay_log_name'
  | RELAY_LOG_POS = relay_log_pos
  | MASTER_DELAY = interval
  | MASTER_SSL = {0|1}
  | MASTER_SSL_CA = 'ca_file_name'
  | MASTER_SSL_CAPATH = 'ca_directory_name'
  | MASTER_SSL_CERT = 'cert_file_name'
  | MASTER_SSL_CRL = 'crl_file_name'
  | MASTER_SSL_CRLPATH = 'crl_directory_name'
  | MASTER_SSL_KEY = 'key_file_name'
  | MASTER_SSL_CIPHER = 'cipher_list'
  | MASTER_SSL_VERIFY_SERVER_CERT = {0|1}
  | MASTER_USE_GTID = {current_pos|slave_pos|no}
  | IGNORE_SERVER_IDS = (server_id_list)
  | DO_DOMAIN_IDS = ([N,..])
  | IGNORE_DOMAIN_IDS = ([N,..])

Description

The CHANGE MASTER statement sets the options that a replica uses to connect to and replicate from a primary.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical to using the channel_name directly after CHANGE MASTER.

Multi-Source Replication

If you are using multi-source replication, then you need to specify a connection name when you execute CHANGE MASTER. There are two ways to do this:

  • Setting the default_master_connection system variable prior to executing CHANGE MASTER.
  • Setting the connection_name parameter when executing CHANGE MASTER.

default_master_connection

SET default_master_connection = 'gandalf';
STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

connection_name

STOP SLAVE 'gandalf';
CHANGE MASTER 'gandalf' TO 
   MASTER_PASSWORD='new3cret';
START SLAVE 'gandalf';

Options

Connection Options

MASTER_USER

The MASTER_USER option for CHANGE MASTER defines the user account that the replica will use to connect to the primary.

This user account will need the REPLICATION SLAVE privilege (or, from MariaDB 10.5.1, the REPLICATION REPLICA on the primary.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret';
START SLAVE;

The maximum length of the MASTER_USER string is 96 characters until MariaDB 10.5, and 128 characters from MariaDB 10.6.

MASTER_PASSWORD

The MASTER_USER option for CHANGE MASTER defines the password that the replica will use to connect to the primary as the user account defined by the MASTER_USER option.

For example:

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

The maximum length of the MASTER_PASSWORD string is 32 characters.

MASTER_HOST

The MASTER_HOST option for CHANGE MASTER defines the hostname or IP address of the primary.

If you set the value of the MASTER_HOST option to the empty string, then that is not the same as not setting the option's value at all. If you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command will fail with an error. In MariaDB 5.3 and before, if you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command would succeed, but the subsequent START SLAVE command would fail.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_HOST='dbserver1.example.com',
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret',
   MASTER_USE_GTID=slave_pos;
START SLAVE;

If you set the value of the MASTER_HOST option in a CHANGE MASTER command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway.

Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.

The maximum length of the MASTER_HOST string is 60 characters until MariaDB 10.5, and 255 characters from MariaDB 10.6.

MASTER_PORT

The MASTER_PORT option for CHANGE MASTER defines the TCP/IP port of the primary.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_HOST='dbserver1.example.com',
   MASTER_PORT=3307,
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret',
   MASTER_USE_GTID=slave_pos;
START SLAVE;

If you set the value of the MASTER_PORT option in a CHANGE MASTER command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway.

Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.

MASTER_CONNECT_RETRY

The MASTER_CONNECT_RETRY option for CHANGE MASTER defines how many seconds that the replica will wait between connection retries. The default is 60.

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_CONNECT_RETRY=20;
START SLAVE;

The number of connection attempts is limited by the master_retry_count option. It can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
master_retry_count=4294967295

MASTER_BIND

The MASTER_BIND option for CHANGE MASTER is only supported by MySQL 5.6.2 and later and by MySQL NDB Cluster 7.3.1 and later. This option is not supported by MariaDB. See MDEV-19248 for more information.

The MASTER_BIND option for CHANGE MASTER can be used on replicas that have multiple network interfaces to choose which network interface the replica will use to connect to the primary.

MASTER_HEARTBEAT_PERIOD

The MASTER_HEARTBEAT_PERIOD option for CHANGE MASTER can be used to set the interval in seconds between replication heartbeats. Whenever the primary's binary log is updated with an event, the waiting period for the next heartbeat is reset.

This option's interval argument has the following characteristics:

  • It is a decimal value with a range of 0 to 4294967 seconds.
  • It has a resolution of hundredths of a second.
  • Its smallest valid non-zero value is 0.001.
  • Its default value is the value of the slave_net_timeout system variable divided by 2.
  • If it's set to 0, then heartbeats are disabled.

Heartbeats are sent by the primary only if there are no unsent events in the binary log file for a period longer than the interval.

If the RESET SLAVE statement is executed, then the heartbeat interval is reset to the default.

If the slave_net_timeout system variable is set to a value that is lower than the current heartbeat interval, then a warning will be issued.

TLS Options

The TLS options are used for providing information about TLS. The options can be set even on replicas that are compiled without TLS support. The TLS options are saved to either the default master.info file or the file that is configured by the master_info_file option, but these TLS options are ignored unless the replica supports TLS.

See Replication with Secure Connections for more information.

MASTER_SSL

The MASTER_SSL option for CHANGE MASTER tells the replica whether to force TLS for the connection. The valid values are 0 or 1.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL=1;
START SLAVE;

MASTER_SSL_CA

The MASTER_SSL_CA option for CHANGE MASTER defines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Certificate Authorities (CAs) for more information.

The maximum length of MASTER_SSL_CA string is 511 characters.

MASTER_SSL_CAPATH

The MASTER_SSL_CAPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CAPATH='/etc/my.cnf.d/certificates/ca/',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Certificate Authorities (CAs) for more information.

The maximum length of MASTER_SSL_CA_PATH string is 511 characters.

MASTER_SSL_CERT

The MASTER_SSL_CERT option for CHANGE MASTER defines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

The maximum length of MASTER_SSL_CERT string is 511 characters.

MASTER_SSL_CRL

The MASTER_SSL_CRL option for CHANGE MASTER defines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path.

This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CRL='/etc/my.cnf.d/certificates/crl.pem';
START SLAVE;

See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.

The maximum length of MASTER_SSL_CRL string is 511 characters.

MASTER_SSL_CRLPATH

The MASTER_SSL_CRLPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this variable needs to be run through the openssl rehash command.

This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CRLPATH='/etc/my.cnf.d/certificates/crl/';
START SLAVE;

See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.

The maximum length of MASTER_SSL_CRL_PATH string is 511 characters.

MASTER_SSL_KEY

The MASTER_SSL_KEY option for CHANGE MASTER defines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

The maximum length of MASTER_SSL_KEY string is 511 characters.

MASTER_SSL_CIPHER

The MASTER_SSL_CIPHER option for CHANGE MASTER defines the list of permitted ciphers or cipher suites to use for TLS. Besides cipher names, if MariaDB was compiled with OpenSSL, this option could be set to "SSLv3" or "TLSv1.2" to allow all SSLv3 or all TLSv1.2 ciphers. Note that the TLSv1.3 ciphers cannot be excluded when using OpenSSL, even by using this option. See Using TLSv1.3 for details. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CIPHER='TLSv1.2';
START SLAVE;

The maximum length of MASTER_SSL_CIPHER string is 511 characters.

MASTER_SSL_VERIFY_SERVER_CERT

The MASTER_SSL_VERIFY_SERVER_CERT option for CHANGE MASTER enables server certificate verification. This option is disabled by default.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Server Certificate Verification for more information.

Binary Log Options

These options are related to the binary log position on the primary.

MASTER_LOG_FILE

The MASTER_LOG_FILE option for CHANGE MASTER can be used along with MASTER_LOG_POS to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.

The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement.

MASTER_LOG_POS

The MASTER_LOG_POS option for CHANGE MASTER can be used along with MASTER_LOG_FILE to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.

The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement.

Relay Log Options

These options are related to the relay log position on the replica.

RELAY_LOG_FILE

The RELAY_LOG_FILE option for CHANGE MASTER can be used along with the RELAY_LOG_POS option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.

The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept.

When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example:

STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
   RELAY_LOG_FILE='slave-relay-bin.006',
   RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;

When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable.

The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.

RELAY_LOG_POS

The RELAY_LOG_POS option for CHANGE MASTER can be used along with the RELAY_LOG_FILE option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.

The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept.

When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example:

STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
   RELAY_LOG_FILE='slave-relay-bin.006',
   RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;

When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable.

The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.

GTID Options

MASTER_USE_GTID

The MASTER_USE_GTID option for CHANGE MASTER can be used to configure the replica to use the global transaction ID (GTID) when connecting to a primary. The possible values are:

  • current_pos - Replicate in GTID mode and use gtid_current_pos as the position to start downloading transactions from the primary.
  • slave_pos - Replicate in GTID mode and use gtid_slave_pos as the position to start downloading transactions from the primary. From MariaDB 10.5.1, replica_pos is an alias for slave_pos.
  • no - Don't replicate in GTID mode.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_USE_GTID = current_pos;
START SLAVE;

Or:

STOP SLAVE;
SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
   MASTER_USE_GTID = slave_pos;
START SLAVE;

Replication Filter Options

Also see Replication filters.

IGNORE_SERVER_IDS

The IGNORE_SERVER_IDS option for CHANGE MASTER can be used to configure a replica to ignore binary log events that originated from certain servers. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of server_id values. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_SERVER_IDS = (3,5);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_SERVER_IDS = ();
START SLAVE;

DO_DOMAIN_IDS

MariaDB starting with 10.1.2

The DO_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2.

The DO_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replica to only apply binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = (1,2);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = ();
START SLAVE;

The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the DO_DOMAIN_IDS option, and the IGNORE_DOMAIN_IDS option was previously set, then you need to clear the value of the IGNORE_DOMAIN_IDS option. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = (), 
   DO_DOMAIN_IDS = (1,2);
START SLAVE;

The DO_DOMAIN_IDS option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option.

IGNORE_DOMAIN_IDS

MariaDB starting with 10.1.2

The IGNORE_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2.

The IGNORE_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replica to ignore binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = ();
START SLAVE;

The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the IGNORE_DOMAIN_IDS option, and the DO_DOMAIN_IDS option was previously set, then you need to clear the value of the DO_DOMAIN_IDS option. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = (), 
   IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;

The IGNORE_DOMAIN_IDS option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option.

Delayed Replication Options

MASTER_DELAY

MariaDB starting with 10.2.3

The MASTER_DELAY option for CHANGE MASTER was first added in MariaDB 10.2.3 to enable delayed replication.

The MASTER_DELAY option for CHANGE MASTER can be used to enable delayed replication. This option specifies the time in seconds (at least) that a replica should lag behind the primary up to a maximum value of 2147483647, or about 68 years. Before executing an event, the replica will first wait, if necessary, until the given time has passed since the event was created on the primary. The result is that the replica will reflect the state of the primary some time back in the past. The default is zero, no delay.

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_DELAY=3600;
START SLAVE;

Changing Option Values

If you don't specify a given option when executing the CHANGE MASTER statement, then the option keeps its old value in most cases. Most of the time, there is no need to specify the options that do not need to change. For example, if the password for the user account that the replica uses to connect to its primary has changed, but no other options need to change, then you can just change the MASTER_PASSWORD option by executing the following commands:

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

There are some cases where options are implicitly reset, such as when the MASTER_HOST and MASTER_PORT options are changed.

Option Persistence

The values of the MASTER_LOG_FILE and MASTER_LOG_POS options (i.e. the binary log position on the primary) and most other options are written to either the default master.info file or the file that is configured by the master_info_file option. The replica's I/O thread keeps this binary log position updated as it downloads events only when MASTER_USE_GTID option is set to NO. Otherwise the file is not updated on a per event basis.

The master_info_file option can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
master_info_file=/mariadb/myserver1-master.info

The values of the RELAY_LOG_FILE and RELAY_LOG_POS options (i.e. the relay log position) are written to either the default relay-log.info file or the file that is configured by the relay_log_info_file system variable. The replica's SQL thread keeps this relay log position updated as it applies events.

The relay_log_info_file system variable can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
relay_log_info_file=/mariadb/myserver1-relay-log.info

GTID Persistence

If the replica is replicating binary log events that contain GTIDs, then the replica's SQL thread will write every GTID that it applies to the mysql.gtid_slave_pos table. This GTID can be inspected and modified through the gtid_slave_pos system variable.

If the replica has the log_slave_updates system variable enabled and if the replica has the binary log enabled, then every write by the replica's SQL thread will also go into the replica's binary log. This means that GTIDs of replicated transactions would be reflected in the value of the gtid_binlog_pos system variable.

Creating a Slave from a Backup

The CHANGE MASTER statement is useful for setting up a replica when you have a backup of the primary and you also have the binary log position or GTID position corresponding to the backup.

After restoring the backup on the replica, you could execute something like this to use the binary log position:

CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

Or you could execute something like this to use the GTID position:

SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
   MASTER_USE_GTID=slave_pos;
START SLAVE;

See Setting up a Replication Slave with Mariabackup for more information on how to do this with Mariabackup.

Example

The following example changes the primary and primary's binary log coordinates. This is used when you want to set up the replica to replicate the primary:

CHANGE MASTER TO
   MASTER_HOST='master2.mycompany.com',
   MASTER_USER='replication',
   MASTER_PASSWORD='bigs3cret',
   MASTER_PORT=3306,
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4,
   MASTER_CONNECT_RETRY=10;
START SLAVE;

See Also

1.1.2.5.2 START SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

START SLAVE ["start-replicaconnection_name"] [thread_type [, thread_type] ... ] [FOR CHANNEL "start-replicaconnection_name"]
START SLAVE ["start-replicaconnection_name"] [SQL_THREAD] UNTIL                
    MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos [FOR CHANNEL "start-replicaconnection_name"]
START SLAVE ["start-replicaconnection_name"] [SQL_THREAD] UNTIL
    RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos [FOR CHANNEL "start-replicaconnection_name"]
START SLAVE ["start-replicaconnection_name"] [SQL_THREAD] UNTIL
    MASTER_GTID_POS = <GTID position> [FOR CHANNEL "start-replicaconnection_name"]
START ALL SLAVES [thread_type [, thread_type]]

START REPLICA ["start-replicaconnection_name"] [thread_type [, thread_type] ... ] -- from 10.5.1
START REPLICA ["start-replicaconnection_name"] [SQL_THREAD] UNTIL                
    MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos -- from 10.5.1
START REPLICA ["start-replicaconnection_name"] [SQL_THREAD] UNTIL
    RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos -- from 10.5.1
START REPLICA ["start-replicaconnection_name"] [SQL_THREAD] UNTIL
    MASTER_GTID_POS = <GTID position> -- from 10.5.1
START ALL REPLICAS [thread_type [, thread_type]] -- from 10.5.1

thread_type: IO_THREAD | SQL_THREAD

Description

START SLAVE (START REPLICA from MariaDB 10.5.1) with no thread_type options starts both of the replica threads (see replication). The I/O thread reads events from the primary server and stores them in the relay log. The SQL thread reads events from the relay log and executes them. START SLAVE requires the SUPER privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege.

If START SLAVE succeeds in starting the replica threads, it returns without any error. However, even in that case, it might be that the replica threads start and then later stop (for example, because they do not manage to connect to the primary or read its binary log, or some other problem). START SLAVE does not warn you about this. You must check the replica's error log for error messages generated by the replica threads, or check that they are running satisfactorily with SHOW SLAVE STATUS (SHOW REPLICA STATUS from MariaDB 10.5.1).

START SLAVE UNTIL

START SLAVE UNTIL refers to the SQL_THREAD replica position at which the SQL_THREAD replication will halt. If SQL_THREAD isn't specified both threads are started.

START SLAVE UNTIL master_gtid_pos=xxx is also supported. See Global Transaction ID/START SLAVE UNTIL master_gtid_pos=xxx for more details.

connection_name

If there is only one nameless primary, or the default primary (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the START SLAVE statement will apply to the specified primary. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after START SLAVE.

START ALL SLAVES

START ALL SLAVES starts all configured replicas (replicas with master_host not empty) that were not started before. It will give a note for all started connections. You can check the notes with SHOW WARNINGS.

START REPLICA

MariaDB starting with 10.5.1

START REPLICA is an alias for START SLAVE from MariaDB 10.5.1.

See Also

1.1.2.5.3 STOP SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

STOP SLAVE ["stop-replicaconnection_name"] [thread_type [, thread_type] ... ] [FOR CHANNEL "stop-replicaconnection_name"]

STOP ALL SLAVES [thread_type [, thread_type]]

STOP REPLICA ["stop-replicaconnection_name"] [thread_type [, thread_type] ... ] -- from 10.5.1

STOP ALL REPLICAS [thread_type [, thread_type]] -- from 10.5.1

thread_type: IO_THREAD | SQL_THREAD

Description

Stops the replica threads. STOP SLAVE requires the SUPER privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege.

Like START SLAVE, this statement may be used with the IO_THREAD and SQL_THREAD options to name the thread or threads to be stopped. In almost all cases, one never need to use the thread_type options.

STOP SLAVE waits until any current replication event group affecting one or more non-transactional tables has finished executing (if there is any such replication group), or until the user issues a KILL QUERY or KILL CONNECTION statement.

Note that STOP SLAVE doesn't delete the connection permanently. Next time you execute START SLAVE or the MariaDB server restarts, the replica connection is restored with it's original arguments. If you want to delete a connection, you should execute RESET SLAVE.

STOP ALL SLAVES

STOP ALL SLAVES stops all your running replicas. It will give you a note for every stopped connection. You can check the notes with SHOW WARNINGS.

connection_name

The connection_name option is used for multi-source replication.

If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the STOP SLAVE statement will apply to the specified master. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after STOP SLAVE.

STOP REPLICA

MariaDB starting with 10.5.1

STOP REPLICA is an alias for STOP SLAVE from MariaDB 10.5.1.

See Also

  • CHANGE MASTER TO is used to create and change connections.
  • START SLAVE is used to start a predefined connection.
  • RESET SLAVE is used to reset parameters for a connection and also to permanently delete a master connection.

1.1.2.5.4 RESET SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

RESET SLAVE ["reset-replicaconnection_name"] [ALL]  [FOR CHANNEL "reset-replicaconnection_name"]              

Description

RESET SLAVE makes the slave forget its replication position in the master's binary log. This statement is meant to be used for a clean start. It deletes the master.info and relay-log.info files, all the relay log files, and starts a new relay log file. To use RESET SLAVE, the slave replication threads must be stopped (use STOP SLAVE if necessary).

Note: All relay log files are deleted, even if they have not been completely executed by the slave SQL thread. (This is a condition likely to exist on a replication slave if you have issued a STOP SLAVE statement or if the slave is highly loaded.)

Note: RESET REPLICA does not reset the global gtid_slave_pos variable. This means that a replica server configured with CHANGE MASTER TO MASTER_USE_GTID=slave_pos will not receive events with GTIDs occurring before the state saved in gtid_slave_pos. If the intent is to reprocess these events, gtid_slave_pos must be manually reset, e.g. by executing set global gtid_slave_pos="".

Connection information stored in the master.info file is immediately reset using any values specified in the corresponding startup options. This information includes values such as master host, master port, master user, and master password. If the slave SQL thread was in the middle of replicating temporary tables when it was stopped, and RESET SLAVE is issued, these replicated temporary tables are deleted on the slave.

The ALL also resets the PORT, HOST, USER and PASSWORD parameters for the slave. If you are using a connection name, it will permanently delete it and it will not show up anymore in SHOW ALL SLAVES STATUS.

connection_name

The connection_name option is used for multi-source replication.

If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the RESET SLAVE statement will apply to the specified master. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after RESET SLAVE.

RESET REPLICA

MariaDB starting with 10.5.1

RESET REPLICA is an alias for RESET SLAVE from MariaDB 10.5.1.

See Also

  • STOP SLAVE stops the slave, but it can be restarted with START SLAVE or after next MariaDB server restart.

1.1.2.5.5 SET GLOBAL SQL_SLAVE_SKIP_COUNTER

Syntax

SET GLOBAL sql_slave_skip_counter = N

Description

This statement skips the next N events from the master. This is useful for recovering from replication stops caused by a statement.

If multi-source replication is used, this statement applies to the default connection. It could be necessary to change the value of the default_master_connection server system variable.

Note that, if the event is a transaction, the whole transaction will be skipped. With non-transactional engines, an event is always a single statement.

This statement is valid only when the slave threads are not running. Otherwise, it produces an error.

The statement does not automatically restart the slave threads.

Example

SHOW SLAVE STATUS \G
...
SET GLOBAL sql_slave_skip_counter = 1;
START SLAVE;

Multi-source replication:

SET @@default_master_connection = 'master_01';
SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
START SLAVE;

Multiple Replication Domains

sql_slave_skip_counter can't be used to skip transactions on a slave if GTID replication is in use and if gtid_slave_pos contains multiple gtid_domain_id values. In that case, you'll get an error like the following:

ERROR 1966 (HY000): When using parallel replication and GTID with multiple 
 replication domains, @@sql_slave_skip_counter can not be used. Instead, 
 setting @@gtid_slave_pos explicitly can be  used to skip to after a given GTID 
 position.

In order to skip transactions in cases like this, you will have to manually change gtid_slave_pos.

See Also

1.1.2.5.6 SHOW RELAYLOG EVENTS

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

SHOW RELAYLOG ['connection_name'] EVENTS
    [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
    [ FOR CHANNEL 'channel_name']

Description

On replicas, this command shows the events in the relay log. If 'log_name' is not specified, the first relay log is shown.

Syntax for the LIMIT clause is the same as for SELECT ... LIMIT.

Using the LIMIT clause is highly recommended because the SHOW RELAYLOG EVENTS command returns the complete contents of the relay log, which can be quite large.

This command does not return events related to setting user and system variables. If you need those, use mariadb-binlog/mysqlbinlog.

On the primary, this command does nothing.

Requires the REPLICA MONITOR privilege (>= MariaDB 10.5.9), the REPLICATION SLAVE ADMIN privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

connection_name

If there is only one nameless primary, or the default primary (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the SHOW RELAYLOG statement will apply to the specified primary. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after SHOW RELAYLOG.

1.1.2.5.7 SHOW SLAVE STATUS

Syntax

SHOW SLAVE ["connection_name"] STATUS [FOR CHANNEL "connection_name"]
SHOW REPLICA ["connection_name"] STATUS -- From MariaDB 10.5.1

or

SHOW ALL SLAVES STATUS
SHOW ALL REPLICAS STATUS -- From MariaDB 10.5.1

Description

This statement is to be run on a replica and provides status information on essential parameters of the replica threads.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege, or, from MariaDB 10.5.9, the REPLICA MONITOR privilege.

Multi-Source

The FULL and "connection_name" options allow you to connect to many primaries at the same time.

ALL SLAVES (or ALL REPLICAS from MariaDB 10.5.1) gives you a list of all connections to the primary nodes.

The rows will be sorted according to Connection_name.

If you specify a connection_name, you only get the information about that connection. If connection_name is not used, then the name set by default_master_connection is used. If the connection name doesn't exist you will get an error: There is no master connection for 'xxx'.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after SHOW SLAVE.

Column Descriptions

NameDescriptionAdded
Connection_nameName of the primary connection. Returned with SHOW ALL SLAVES STATUS (or SHOW ALL REPLICAS STATUS from MariaDB 10.5.1) only.
Slave_SQL_StateState of SQL thread. Returned with SHOW ALL SLAVES STATUS (or SHOW ALL REPLICAS STATUS from MariaDB 10.5.1) only. See Slave SQL Thread States.
Slave_IO_StateState of I/O thread. See Slave I/O Thread States.
Master_hostMaster host that the replica is connected to.
Master_userAccount user name being used to connect to the primary.
Master_portThe port being used to connect to the primary.
Connect_RetryTime in seconds between retries to connect. The default is 60. The CHANGE MASTER TO statement can set this. The master-retry-count option determines the maximum number of reconnection attempts.
Master_Log_FileName of the primary binary log file that the I/O thread is currently reading from.
Read_Master_Log_PosPosition up to which the I/O thread has read in the current primary binary log file.
Relay_Log_FileName of the relay log file that the SQL thread is currently processing.
Relay_Log_PosPosition up to which the SQL thread has finished processing in the current relay log file.
Relay_Master_Log_FileName of the primary binary log file that contains the most recent event executed by the SQL thread.
Slave_IO_RunningWhether the replica I/O thread is running and connected (Yes), running but not connected to a primary (Connecting) or not running (No).
Slave_SQL_RunningWhether or not the SQL thread is running.
Replicate_Do_DBDatabases specified for replicating with the replicate_do_db option.
Replicate_Ignore_DBDatabases specified for ignoring with the replicate_ignore_db option.
Replicate_Do_TableTables specified for replicating with the replicate_do_table option.
Replicate_Ignore_TableTables specified for ignoring with the replicate_ignore_table option.
Replicate_Wild_Do_TableTables specified for replicating with the replicate_wild_do_table option.
Replicate_Wild_Ignore_TableTables specified for ignoring with the replicate_wild_ignore_table option.
Last_ErrnoAlias for Last_SQL_Errno (see below)
Last ErrorAlias for Last_SQL_Error (see below)
Skip_CounterNumber of events that a replica skips from the master, as recorded in the sql_slave_skip_counter system variable.
Exec_Master_Log_PosPosition up to which the SQL thread has processed in the current master binary log file. Can be used to start a new replica from a current replica with the CHANGE MASTER TO ... MASTER_LOG_POS option.
Relay_Log_SpaceTotal size of all relay log files combined.
Until_Condition
Until_Log_FileThe MASTER_LOG_FILE value of the START SLAVE UNTIL condition.
Until_Log_PosThe MASTER_LOG_POS value of the START SLAVE UNTIL condition.
Master_SSL_AllowedWhether an SSL connection is permitted (Yes), not permitted (No) or permitted but without the replica having SSL support enabled (Ignored)
Master_SSL_CA_FileThe MASTER_SSL_CA option of the CHANGE MASTER TO statement.
Master_SSL_CA_PathThe MASTER_SSL_CAPATH option of the CHANGE MASTER TO statement.
Master_SSL_CertThe MASTER_SSL_CERT option of the CHANGE MASTER TO statement.
Master_SSL_CipherThe MASTER_SSL_CIPHER option of the CHANGE MASTER TO statement.
Master_SSL_KeyThe MASTER_SSL_KEY option of the CHANGE MASTER TO statement.
Seconds_Behind_MasterDifference between the timestamp logged on the master for the event that the replica is currently processing, and the current timestamp on the replica. Zero if the replica is not currently processing an event. From MariaDB 10.0.23 and MariaDB 10.1.9, with parallel replication, seconds_behind_master is updated only after transactions commit.
Master_SSL_Verify_Server_CertThe MASTER_SSL_VERIFY_SERVER_CERT option of the CHANGE MASTER TO statement.
Last_IO_ErrnoError code of the most recent error that caused the I/O thread to stop (also recorded in the replica's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_IO_ErrorError message of the most recent error that caused the I/O thread to stop (also recorded in the replica's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_SQL_ErrnoError code of the most recent error that caused the SQL thread to stop (also recorded in the replica's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_SQL_ErrorError message of the most recent error that caused the SQL thread to stop (also recorded in the replica's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value.
Replicate_Ignore_Server_IdsList of server_ids that are currently being ignored for replication purposes, or an empty string for none, as specified in the IGNORE_SERVER_IDS option of the CHANGE MASTER TO statement.
Master_Server_IdThe master's server_id value.
Master_SSL_CrlThe MASTER_SSL_CRL option of the CHANGE MASTER TO statement.MariaDB 10.0
Master_SSL_CrlpathThe MASTER_SSL_CRLPATH option of the CHANGE MASTER TO statement.MariaDB 10.0
Using_GtidWhether or not global transaction ID's are being used for replication (can be No, Slave_Pos, or Current_Pos).MariaDB 10.0.2
Gtid_IO_PosCurrent global transaction ID value.MariaDB 10.0.2
Retried_transactionsNumber of retried transactions for this connection. Returned with SHOW ALL SLAVES STATUS only.
Max_relay_log_sizeMax relay log size for this connection. Returned with SHOW ALL SLAVES STATUS only.
Executed_log_entriesHow many log entries the replica has executed. Returned with SHOW ALL SLAVES STATUS only.
Slave_received_heartbeatsHow many heartbeats we have got from the master. Returned with SHOW ALL SLAVES STATUS only.
Slave_heartbeat_periodHow often to request a heartbeat packet from the master (in seconds). Returned with SHOW ALL SLAVES STATUS only.
Gtid_Slave_PosGTID of the last event group replicated on a replica server, for each replication domain, as stored in the gtid_slave_pos system variable. Returned with SHOW ALL SLAVES STATUS only.
SQL_DelayValue specified by MASTER_DELAY in CHANGE MASTER (or 0 if none).MariaDB 10.2.3
SQL_Remaining_DelayWhen the replica is delaying the execution of an event due to MASTER_DELAY, this is the number of seconds of delay remaining before the event will be applied. Otherwise, the value is NULL.MariaDB 10.2.3
Slave_SQL_Running_StateThe state of the SQL driver threads, same as in SHOW PROCESSLIST. When the replica is delaying the execution of an event due to MASTER_DELAY, this field displays: "Waiting until MASTER_DELAY seconds after master executed event".MariaDB 10.2.3
Slave_DDL_GroupsThis status variable counts the occurrence of DDL statements. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7
Slave_Non_Transactional_GroupsThis status variable counts the occurrence of non-transactional event groups. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7
Slave_Transactional_GroupsThis status variable counts the occurrence of transactional event groups. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7

SHOW REPLICA STATUS

MariaDB starting with 10.5.1

SHOW REPLICA STATUS is an alias for SHOW SLAVE STATUS from MariaDB 10.5.1.

Examples

If you issue this statement using the mysql client, you can use a \G statement terminator rather than a semicolon to obtain a more readable vertical layout.

SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: db01.example.com
                  Master_User: replicant
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mariadb-bin.000010
          Read_Master_Log_Pos: 548
               Relay_Log_File: relay-bin.000004
                Relay_Log_Pos: 837
        Relay_Master_Log_File: mariadb-bin.000010
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 548
              Relay_Log_Space: 1497
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 101
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
SHOW ALL SLAVES STATUS\G
*************************** 1. row ***************************
              Connection_name: 
              Slave_SQL_State: Slave has read all relay log; waiting for the slave I/O thread to update it
               Slave_IO_State: Waiting for master to send event
                  Master_Host: db01.example.com
                  Master_User: replicant
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mariadb-bin.000010
          Read_Master_Log_Pos: 3608
               Relay_Log_File: relay-bin.000004
                Relay_Log_Pos: 3897
        Relay_Master_Log_File: mariadb-bin.000010
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 3608
              Relay_Log_Space: 4557
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 101
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos:
         Retried_transactions: 0
           Max_relay_log_size: 104857600
         Executed_log_entries: 40
    Slave_received_heartbeats: 11
       Slave_heartbeat_period: 1800.000
               Gtid_Slave_Pos: 0-101-2320

You can also access some of the variables directly from status variables:

SET @@default_master_connection="test" ;
show status like "%slave%"

Variable_name   Value
Com_show_slave_hosts    0
Com_show_slave_status   0
Com_start_all_slaves    0
Com_start_slave 0
Com_stop_all_slaves     0
Com_stop_slave  0
Rpl_semi_sync_slave_status      OFF
Slave_connections       0
Slave_heartbeat_period  1800.000
Slave_open_temp_tables  0
Slave_received_heartbeats       0
Slave_retried_transactions      0
Slave_running   OFF
Slaves_connected        0
Slaves_running  1

See Also

1.1.2.5.8 SHOW MASTER STATUS

Syntax

SHOW MASTER STATUS
SHOW BINLOG STATUS -- From MariaDB 10.5.2

Description

Provides status information about the binary log files of the primary.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the BINLOG MONITOR privilege.

To see information about the current GTIDs in the binary log, use the gtid_binlog_pos variable.

SHOW MASTER STATUS was renamed to SHOW BINLOG STATUS in MariaDB 10.5.2, but the old name remains an alias for compatibility purposes.

Example

SHOW MASTER STATUS;
+--------------------+----------+--------------+------------------+
| File               | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| mariadb-bin.000016 |      475 |              |                  |
+--------------------+----------+--------------+------------------+
SELECT @@global.gtid_binlog_pos;
+--------------------------+
| @@global.gtid_binlog_pos |
+--------------------------+
| 0-1-2                    |
+--------------------------+

See Also

1.1.2.5.9 SHOW SLAVE HOSTS

Syntax

SHOW SLAVE HOSTS
SHOW REPLICA HOSTS -- from MariaDB 10.5.1

Description

This command is run on the primary and displays a list of replicas that are currently registered with it. Only replicas started with the --report-host=host_name option are visible in this list.

The list is displayed on any server (not just the primary server). The output looks like this:

SHOW SLAVE HOSTS;
+------------+-----------+------+-----------+
| Server_id  | Host      | Port | Master_id |
+------------+-----------+------+-----------+
|  192168010 | iconnect2 | 3306 | 192168011 |
| 1921680101 | athena    | 3306 | 192168011 |
+------------+-----------+------+-----------+
  • Server_id: The unique server ID of the replica server, as configured in the server's option file, or on the command line with --server-id=value.
  • Host: The host name of the replica server, as configured in the server's option file, or on the command line with --report-host=host_name. Note that this can differ from the machine name as configured in the operating system.
  • Port: The port the replica server is listening on.
  • Master_id: The unique server ID of the primary server that the replica server is replicating from.

Some MariaDB and MySQL versions report another variable, rpl_recovery_rank. This variable was never used, and was eventually removed in MariaDB 10.1.2 .

Requires the REPLICATION MASTER ADMIN privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

SHOW REPLICA HOSTS

MariaDB starting with 10.5.1

SHOW REPLICA HOSTS is an alias for SHOW SLAVE HOSTS from MariaDB 10.5.1.

See Also

1.1.2.5.10 RESET MASTER

RESET MASTER [TO #]

Deletes all binary log files listed in the index file, resets the binary log index file to be empty, and creates a new binary log file with a suffix of .000001.

If TO # is given, then the first new binary log file will start from number #.

This statement is for use only when the master is started for the first time, and should never be used if any slaves are actively replicating from the binary log.

See Also

1.1.2.6 Plugin SQL Statements

1.1.2.6.1 SHOW PLUGINS

Syntax

SHOW PLUGINS;

Description

SHOW PLUGINS displays information about installed plugins. The Library column indicates the plugin library - if it is NULL, the plugin is built-in and cannot be uninstalled.

The PLUGINS table in the information_schema database contains more detailed information.

For specific information about storage engines (a particular type of plugin), see the information_schema.ENGINES table and the SHOW ENGINES statement.

Examples

SHOW PLUGINS;
+----------------------------+----------+--------------------+-------------+---------+
| Name                       | Status   | Type               | Library     | License |
+----------------------------+----------+--------------------+-------------+---------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| mysql_native_password      | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| mysql_old_password         | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| MRG_MyISAM                 | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MyISAM                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| CSV                        | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MEMORY                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEDERATED                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| PERFORMANCE_SCHEMA         | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| Aria                       | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| InnoDB                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| INNODB_TRX                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
...
| INNODB_SYS_FOREIGN         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN_COLS    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| SPHINX                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| ARCHIVE                    | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| BLACKHOLE                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEEDBACK                   | DISABLED | INFORMATION SCHEMA | NULL        | GPL     |
| partition                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| pam                        | ACTIVE   | AUTHENTICATION     | auth_pam.so | GPL     |
+----------------------------+----------+--------------------+-------------+---------+

See Also

1.1.2.6.2 SHOW PLUGINS SONAME

Syntax

SHOW PLUGINS SONAME { library | LIKE 'pattern' | WHERE expr };

Description

SHOW PLUGINS SONAME displays information about compiled-in and all server plugins in the plugin_dir directory, including plugins that haven't been installed.

Examples

SHOW PLUGINS SONAME 'ha_example.so';
+----------+---------------+----------------+---------------+---------+
| Name     | Status        | Type           | Library       | License |
+----------+---------------+----------------+---------------+---------+
| EXAMPLE  | NOT INSTALLED | STORAGE ENGINE | ha_example.so | GPL     |
| UNUSABLE | NOT INSTALLED | DAEMON         | ha_example.so | GPL     |
+----------+---------------+----------------+---------------+---------+

There is also a corresponding information_schema table, called ALL_PLUGINS, which contains more complete information.

1.1.2.6.3 INSTALL PLUGIN

Syntax

INSTALL PLUGIN [IF NOT EXISTS] plugin_name SONAME 'plugin_library'

Description

This statement installs an individual plugin from the specified library. To install the whole library (which could be required), use INSTALL SONAME. See also Installing a Plugin.

plugin_name is the name of the plugin as defined in the plugin declaration structure contained in the library file. Plugin names are not case sensitive. For maximal compatibility, plugin names should be limited to ASCII letters, digits, and underscore, because they are used in C source files, shell command lines, M4 and Bourne shell scripts, and SQL environments.

plugin_library is the name of the shared library that contains the plugin code. The file name extension can be omitted (which makes the statement look the same on all architectures).

The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file:

[mysqld] plugin_dir=/path/to/plugin/directory

If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable).

INSTALL PLUGIN adds a line to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name.

INSTALL PLUGIN causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart.

INSTALL PLUGIN also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used.

To use INSTALL PLUGIN, you must have the INSERT privilege for the mysql.plugin table.

At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL PLUGIN only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option.

When the server shuts down, it executes the de-initialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup.

If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option.

MariaDB starting with 10.4.0

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a note instead of an error if the specified plugin already exists. See SHOW WARNINGS.

Examples

INSTALL PLUGIN sphinx SONAME 'ha_sphinx.so';

The extension can also be omitted:

INSTALL PLUGIN innodb SONAME 'ha_xtradb';

From MariaDB 10.4.0:

INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected (0.104 sec)

INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message                            |
+-------+------+------------------------------------+
| Note  | 1968 | Plugin 'example' already installed |
+-------+------+------------------------------------+

See Also

1.1.2.6.4 UNINSTALL PLUGIN

Syntax

UNINSTALL PLUGIN [IF EXISTS] plugin_name

Description

This statement removes a single installed plugin. To uninstall the whole library which contains the plugin, use UNINSTALL SONAME. You cannot uninstall a plugin if any table that uses it is open.

plugin_name must be the name of some plugin that is listed in the mysql.plugin table. The server executes the plugin's deinitialization function and removes the row for the plugin from the mysql.plugin table, so that subsequent server restarts will not load and initialize the plugin. UNINSTALL PLUGIN does not remove the plugin's shared library file.

To use UNINSTALL PLUGIN, you must have the DELETE privilege for the mysql.plugin table.

MariaDB starting with 10.4.0

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin does not exist. See SHOW WARNINGS.

Examples

UNINSTALL PLUGIN example;

From MariaDB 10.4.0:

UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected (0.099 sec)

UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message                       |
+-------+------+-------------------------------+
| Note  | 1305 | PLUGIN example does not exist |
+-------+------+-------------------------------+

See Also

1.1.2.6.5 INSTALL SONAME

Syntax

INSTALL SONAME 'plugin_library'

Description

This statement is a variant of INSTALL PLUGIN. It installs all plugins from a given plugin_library. See INSTALL PLUGIN for details.

plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures).

The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file:

[mysqld] plugin_dir=/path/to/plugin/directory

If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable).

INSTALL SONAME adds one or more lines to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name.

INSTALL SONAME causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart.

INSTALL SONAME also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used.

To use INSTALL SONAME, you must have the INSERT privilege for the mysql.plugin table.

At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL SONAME only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option.

When the server shuts down, it executes the de-initialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup.

If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option.

If you need to install only one plugin from a library, use the INSTALL PLUGIN statement.

Examples

To load the XtraDB storage engine and all of its information_schema tables with one statement, use

INSTALL SONAME 'ha_xtradb';

This statement can be used instead of INSTALL PLUGIN even when the library contains only one plugin:

INSTALL SONAME 'ha_sequence';

See Also

1.1.2.6.6 UNINSTALL SONAME

Syntax

UNINSTALL SONAME [IF EXISTS] 'plugin_library'

Description

This statement is a variant of UNINSTALL PLUGIN statement, that removes all plugins belonging to a specified plugin_library. See UNINSTALL PLUGIN for details.

plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures).

To use UNINSTALL SONAME, you must have the DELETE privilege for the mysql.plugin table.

MariaDB starting with 10.4.0

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin library does not exist. See SHOW WARNINGS.

Examples

To uninstall the XtraDB plugin and all of its information_schema tables with one statement, use

UNINSTALL SONAME 'ha_xtradb';

From MariaDB 10.4.0:

UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected (0.099 sec)

UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+-------------------------------------+
| Level | Code | Message                             |
+-------+------+-------------------------------------+
| Note  | 1305 | SONAME ha_example.so does not exist |
+-------+------+-------------------------------------+

See Also

1.1.2.6.7 mysql_plugin

MariaDB starting with 10.4.6

From MariaDB 10.4.6, mariadb-plugin is a symlink to mysql_plugin.

MariaDB starting with 10.5.2

From MariaDB 10.5.2, mysql_plugin is the symlink, and mariadb-plugin the binary name.

mysql_plugin is a tool for enabling or disabling plugins.

It is a commandline alternative to the INSTALL PLUGIN and UNINSTALL PLUGIN statements, and the --plugin-load option to mysqld.

mysql_plugin must be run while the server is offline, and works by adding or removing rows from the mysql.plugin table.

Usage

mysql_plugin [options] <plugin> ENABLE|DISABLE

mysql_plugin expects to find a configuration file that indicates how to configure the plugins. The configuration file is by default the same name as the plugin, with a .ini extension. For example:

mysql_plugin crazyplugins ENABLE

Here, mysql_plugin will look for a file called crazyplugins.ini

crazyplugins
crazyplugin1
crazyplugin2
crazyplugin3

The first line should contain the name of the library object file, with no extension. The other lines list the names of the components. Each value should be on a separate line, and the # character at the start of the line indicates a comment.

Options

The following options can be specified on the command line, while some can be specified in the [mysqld] group of any option file. For options specified in a [mysqld] group, only the --basedir, --datadir, and --plugin-dir options can be used - the rest are ignored.

OptionDescription
-b, --basedir=nameThe base directory for the server.
-d, --datadir=nameThe data directory for the server.
-?, --helpDisplay help and exit.
-f, --my-print-defaults=namePath to my_print_defaults executable. Example: /source/temp11/extra
-m, --mysqld=namePath to mysqld executable. Example: /sbin/temp1/mysql/bin
-n, --no-defaultsDo not read values from configuration file.
-p, --plugin-dir=nameThe plugin directory for the server.
-i, --plugin-ini=nameRead plugin information from configuration file specified instead of from <plugin-dir>/<plugin_name>.ini.
-P, --print-defaultsShow default values from configuration file.
-v, --verboseMore verbose output; you can use this multiple times to get even more verbose output.
-V, --versionOutput version information and exit.

See Also

1.1.2.7 SET Commands

1.1.2.7.1 SET

Syntax

SET variable_assignment [, variable_assignment] ...

variable_assignment:
      user_var_name = expr
    | [GLOBAL | SESSION] system_var_name = expr
    | [@@global. | @@session. | @@]system_var_name = expr

One can also set a user variable in any expression with this syntax:

user_var_name:= expr

Description

The SET statement assigns values to different types of variables that affect the operation of the server or your client. Older versions of MySQL employed SET OPTION, but this syntax was deprecated in favor of SET without OPTION, and was removed in MariaDB 10.0.

Changing a system variable by using the SET statement does not make the change permanently. To do so, the change must be made in a configuration file.

For setting variables on a per-query basis (from MariaDB 10.1.2), see SET STATEMENT.

See SHOW VARIABLES for documentation on viewing server system variables.

See Server System Variables for a list of all the system variables.

GLOBAL / SESSION

When setting a system variable, the scope can be specified as either GLOBAL or SESSION.

A global variable change affects all new sessions. It does not affect any currently open sessions, including the one that made the change.

A session variable change affects the current session only.

If the variable has a session value, not specifying either GLOBAL or SESSION will be the same as specifying SESSION. If the variable only has a global value, not specifying GLOBAL or SESSION will apply to the change to the global value.

DEFAULT

Setting a global variable to DEFAULT will restore it to the server default, and setting a session variable to DEFAULT will restore it to the current global value.

Examples

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 64           |
| SKIP_PARALLEL_REPLICATION | OFF           | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

Setting the session values:

SET max_error_count=128;Query OK, 0 rows affected (0.000 sec)

SET skip_parallel_replication=ON;Query OK, 0 rows affected (0.000 sec)

SET innodb_sync_spin_loops=60;
ERROR 1229 (HY000): Variable 'innodb_sync_spin_loops' is a GLOBAL variable 
  and should be set with SET GLOBAL

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 128           | 64           |
| SKIP_PARALLEL_REPLICATION | ON            | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

Setting the global values:

SET GLOBAL max_error_count=256;

SET GLOBAL skip_parallel_replication=ON;
ERROR 1228 (HY000): Variable 'skip_parallel_replication' is a SESSION variable 
  and can't be used with SET GLOBAL

SET GLOBAL innodb_sync_spin_loops=120;

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 128           | 256          |
| SKIP_PARALLEL_REPLICATION | ON            | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 120          |
+---------------------------+---------------+--------------+

SHOW VARIABLES will by default return the session value unless the variable is global only.

SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 128   |
+-----------------+-------+

SHOW VARIABLES LIKE 'skip_parallel_replication';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| skip_parallel_replication | ON    |
+---------------------------+-------+

SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 120   |
+------------------------+-------+

Using the inplace syntax:

SELECT (@a:=1);
+---------+
| (@a:=1) |
+---------+
|       1 |
+---------+

SELECT @a;
+------+
| @a   |
+------+
|    1 |
+------+

See Also

1.1.2.7.2 SET CHARACTER SET

Syntax

SET {CHARACTER SET | CHARSET}
    {charset_name | DEFAULT}

Description

Sets the character_set_client and character_set_results session system variables to the specified character set and collation_connection to the value of collation_database, which implicitly sets character_set_connection to the value of character_set_database.

This maps all strings sent between the current client and the server with the given mapping.

Example

SHOW VARIABLES LIKE 'character_set\_%';
+--------------------------+--------+
| Variable_name            | Value  |
+--------------------------+--------+
| character_set_client     | utf8   |
| character_set_connection | utf8   |
| character_set_database   | latin1 |
| character_set_filesystem | binary |
| character_set_results    | utf8   |
| character_set_server     | latin1 |
| character_set_system     | utf8   |
+--------------------------+--------+

SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | utf8_general_ci   |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+

SET CHARACTER SET utf8mb4;

SHOW VARIABLES LIKE 'character_set\_%';
+--------------------------+---------+
| Variable_name            | Value   |
+--------------------------+---------+
| character_set_client     | utf8mb4 |
| character_set_connection | latin1  |
| character_set_database   | latin1  |
| character_set_filesystem | binary  |
| character_set_results    | utf8mb4 |
| character_set_server     | latin1  |
| character_set_system     | utf8    |
+--------------------------+---------+

SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | latin1_swedish_ci |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+

See Also

1.1.2.7.3 SET GLOBAL SQL_SLAVE_SKIP_COUNTER

Syntax

SET GLOBAL sql_slave_skip_counter = N

Description

This statement skips the next N events from the master. This is useful for recovering from replication stops caused by a statement.

If multi-source replication is used, this statement applies to the default connection. It could be necessary to change the value of the default_master_connection server system variable.

Note that, if the event is a transaction, the whole transaction will be skipped. With non-transactional engines, an event is always a single statement.

This statement is valid only when the slave threads are not running. Otherwise, it produces an error.

The statement does not automatically restart the slave threads.

Example

SHOW SLAVE STATUS \G
...
SET GLOBAL sql_slave_skip_counter = 1;
START SLAVE;

Multi-source replication:

SET @@default_master_connection = 'master_01';
SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
START SLAVE;

Multiple Replication Domains

sql_slave_skip_counter can't be used to skip transactions on a slave if GTID replication is in use and if gtid_slave_pos contains multiple gtid_domain_id values. In that case, you'll get an error like the following:

ERROR 1966 (HY000): When using parallel replication and GTID with multiple 
 replication domains, @@sql_slave_skip_counter can not be used. Instead, 
 setting @@gtid_slave_pos explicitly can be  used to skip to after a given GTID 
 position.

In order to skip transactions in cases like this, you will have to manually change gtid_slave_pos.

See Also

1.1.2.7.4 SET NAMES

Syntax

SET NAMES {'charset_name'
    [COLLATE 'collation_name'] | DEFAULT}

Description

Sets the character_set_client, character_set_connection, character_set_results and, implicitly, the collation_connection session system variables to the specified character set and collation.

This determines which character set the client will use to send statements to the server, and the server will use for sending results back to the client.

ucs2, utf16, and utf32 are not valid character sets for SET NAMES, as they cannot be used as client character sets.

The collation clause is optional. If not defined (or if DEFAULT is specified), the default collation for the character set will be used.

Quotes are optional for the character set or collation clauses.

Examples

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-----------------+
| VARIABLE_NAME            | SESSION_VALUE   |
+--------------------------+-----------------+
| CHARACTER_SET_RESULTS    | utf8            |
| CHARACTER_SET_CONNECTION | utf8            |
| CHARACTER_SET_CLIENT     | utf8            |
| COLLATION_CONNECTION     | utf8_general_ci |
+--------------------------+-----------------+

SET NAMES big5;

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-----------------+
| VARIABLE_NAME            | SESSION_VALUE   |
+--------------------------+-----------------+
| CHARACTER_SET_RESULTS    | big5            |
| CHARACTER_SET_CONNECTION | big5            |
| CHARACTER_SET_CLIENT     | big5            |
| COLLATION_CONNECTION     | big5_chinese_ci |
+--------------------------+-----------------+

SET NAMES 'latin1' COLLATE 'latin1_bin';

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+---------------+
| VARIABLE_NAME            | SESSION_VALUE |
+--------------------------+---------------+
| CHARACTER_SET_RESULTS    | latin1        |
| CHARACTER_SET_CONNECTION | latin1        |
| CHARACTER_SET_CLIENT     | latin1        |
| COLLATION_CONNECTION     | latin1_bin    |
+--------------------------+---------------+

SET NAMES DEFAULT;

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-------------------+
| VARIABLE_NAME            | SESSION_VALUE     |
+--------------------------+-------------------+
| CHARACTER_SET_RESULTS    | latin1            |
| CHARACTER_SET_CONNECTION | latin1            |
| CHARACTER_SET_CLIENT     | latin1            |
| COLLATION_CONNECTION     | latin1_swedish_ci |
+--------------------------+-------------------+

See Also

1.1.2.7.5 SET PASSWORD

Syntax

SET PASSWORD [FOR user] =
    {
        PASSWORD('some password')
      | OLD_PASSWORD('some password')
      | 'encrypted password'
    }

Description

The SET PASSWORD statement assigns a password to an existing MariaDB user account.

If the password is specified using the PASSWORD() or OLD_PASSWORD() function, the literal text of the password should be given. If the password is specified without using either function, the password should be the already-encrypted password value as returned by PASSWORD().

OLD_PASSWORD() should only be used if your MariaDB/MySQL clients are very old (< 4.0.0).

With no FOR clause, this statement sets the password for the current user. Any client that has connected to the server using a non-anonymous account can change the password for that account.

With a FOR clause, this statement sets the password for a specific account on the current server host. Only clients that have the UPDATE privilege for the mysql database can do this. The user value should be given in user_name@host_name format, where user_name and host_name are exactly as they are listed in the User and Host columns of the mysql.user table entry.

The argument to PASSWORD() and the password given to MariaDB clients can be of arbitrary length.

Authentication Plugin Support

MariaDB starting with 10.4

In MariaDB 10.4 and later, SET PASSWORD (with or without PASSWORD()) works for accounts authenticated via any authentication plugin that supports passwords stored in the mysql.global_priv table.

The ed25519, mysql_native_password, and mysql_old_password authentication plugins store passwords in the mysql.global_priv table.

If you run SET PASSWORD on an account that authenticates with one of these authentication plugins that stores passwords in the mysql.global_priv table, then the PASSWORD() function is evaluated by the specific authentication plugin used by the account. The authentication plugin hashes the password with a method that is compatible with that specific authentication plugin.

The unix_socket, named_pipe, gssapi, and pam authentication plugins do not store passwords in the mysql.global_priv table. These authentication plugins rely on other methods to authenticate the user.

If you attempt to run SET PASSWORD on an account that authenticates with one of these authentication plugins that doesn't store a password in the mysql.global_priv table, then MariaDB Server will raise a warning like the following:

SET PASSWORD is ignored for users authenticating via unix_socket plugin

See Authentication from MariaDB 10.4 for an overview of authentication changes in MariaDB 10.4.

MariaDB until 10.3

In MariaDB 10.3 and before, SET PASSWORD (with or without PASSWORD()) only works for accounts authenticated via mysql_native_password or mysql_old_password authentication plugins

Passwordless User Accounts

User accounts do not always require passwords to login.

The unix_socket , named_pipe and gssapi authentication plugins do not require a password to authenticate the user.

The pam authentication plugin may or may not require a password to authenticate the user, depending on the specific configuration.

The mysql_native_password and mysql_old_password authentication plugins require passwords for authentication, but the password can be blank. In that case, no password is required.

If you provide a password while attempting to log into the server as an account that doesn't require a password, then MariaDB server will simply ignore the password.

MariaDB starting with 10.4

In MariaDB 10.4 and later, a user account can be defined to use multiple authentication plugins in a specific order of preference. This specific scenario may be more noticeable in these versions, since an account could be associated with some authentication plugins that require a password, and some that do not.

Example

For example, if you had an entry with User and Host column values of 'bob' and '%.loc.gov', you would write the statement like this:

SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

If you want to delete a password for a user, you would do:

SET PASSWORD FOR 'bob'@localhost = PASSWORD("");

See Also

1.1.2.7.6 SET ROLE

Syntax

SET ROLE { role | NONE }

Description

The SET ROLE statement enables a role, along with all of its associated permissions, for the current session. To unset a role, use NONE .

If a role that doesn't exist, or to which the user has not been assigned, is specified, an ERROR 1959 (OP000): Invalid role specification error occurs.

An automatic SET ROLE is implicitly performed when a user connects if that user has been assigned a default role. See SET DEFAULT ROLE.

Example

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE staff;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff        |
+--------------+

SET ROLE NONE;

SELECT CURRENT_ROLE();
+----------------+
| CURRENT_ROLE() |
+----------------+
| NULL           |
+----------------+

1.1.2.7.7 SET SQL_LOG_BIN

Syntax

SET [SESSION] sql_log_bin = {0|1}

Description

Sets the sql_log_bin system variable, which disables or enables binary logging for the current connection, if the client has the SUPER privilege. The statement is refused with an error if the client does not have that privilege.

Before MariaDB 5.5 and before MySQL 5.6 one could also set sql_log_bin as a global variable. This has now been disabled as this was too dangerous as it could damage replication.

1.1.2.7.8 SET STATEMENT

MariaDB starting with 10.1.2

Per-query variables were introduced in MariaDB 10.1.2

SET STATEMENT can be used to set the value of a system variable for the duration of the statement. It is also possible to set multiple variables.

Syntax

SET STATEMENT var1=value1 [, var2=value2, ...] 
  FOR <statement>

where varN is a system variable (list of allowed variables is provided below), and valueN is a constant literal.

Description

SET STATEMENT var1=value1 FOR stmt

is roughly equivalent to

SET @save_value=@@var1;
SET SESSION var1=value1;
stmt;
SET SESSION var1=@save_value;

The server parses the whole statement before executing it, so any variables set in this fashion that affect the parser may not have the expected effect. Examples include the charset variables, sql_mode=ansi_quotes, etc.

Examples

One can limit statement execution time max_statement_time:

SET STATEMENT max_statement_time=1000 FOR SELECT ... ;

One can switch on/off individual optimizations:

SET STATEMENT optimizer_switch='materialization=off' FOR SELECT ....;

It is possible to enable MRR/BKA for a query:

SET STATEMENT  join_cache_level=6, optimizer_switch='mrr=on'  FOR SELECT ...

Note that it makes no sense to try to set a session variable inside a SET STATEMENT:

#USELESS STATEMENT
SET STATEMENT sort_buffer_size = 100000 for SET SESSION sort_buffer_size = 200000;

For the above, after setting sort_buffer_size to 200000 it will be reset to its original state (the state before the SET STATEMENT started) after the statement execution.

Limitations

There are a number of variables that cannot be set on per-query basis. These include:

  • autocommit
  • character_set_client
  • character_set_connection
  • character_set_filesystem
  • collation_connection
  • default_master_connection
  • debug_sync
  • interactive_timeout
  • gtid_domain_id
  • last_insert_id
  • log_slow_filter
  • log_slow_rate_limit
  • log_slow_verbosity
  • long_query_time
  • min_examined_row_limit
  • profiling
  • profiling_history_size
  • query_cache_type
  • rand_seed1
  • rand_seed2
  • skip_replication
  • slow_query_log
  • sql_log_off
  • tx_isolation
  • wait_timeout

Source

  • The feature was originally implemented as a Google Summer of Code 2009 project by Joseph Lukas.
  • Percona Server 5.6 included it as Per-query variable statement
  • MariaDB ported the patch and fixed many bugs. The task in MariaDB Jira is MDEV-5231.

1.1.2.7.9 SET TRANSACTION

Syntax

SET [GLOBAL | SESSION] TRANSACTION
    transaction_property [, transaction_property] ...

transaction_property:
    ISOLATION LEVEL level
  | READ WRITE
  | READ ONLY

level:
     REPEATABLE READ
   | READ COMMITTED
   | READ UNCOMMITTED
   | SERIALIZABLE

Description

This statement sets the transaction isolation level or the transaction access mode globally, for the current session, or for the next transaction:

  • With the GLOBAL keyword, the statement sets the default transaction level globally for all subsequent sessions. Existing sessions are unaffected.
  • With the SESSION keyword, the statement sets the default transaction level for all subsequent transactions performed within the current session.
  • Without any SESSION or GLOBAL keyword, the statement sets the isolation level for the next (not started) transaction performed within the current session.

A change to the global default isolation level requires the SUPER privilege. Any session is free to change its session isolation level (even in the middle of a transaction), or the isolation level for its next transaction.

Isolation Level

To set the global default isolation level at server startup, use the --transaction-isolation=level option on the command line or in an option file. Values of level for this option use dashes rather than spaces, so the allowable values are READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. For example, to set the default isolation level to REPEATABLE READ, use these lines in the [mysqld] section of an option file:

[mysqld] transaction-isolation = REPEATABLE-READ

To determine the global and session transaction isolation levels at runtime, check the value of the tx_isolation system variable:

SELECT @@GLOBAL.tx_isolation, @@tx_isolation;

InnoDB supports each of the translation isolation levels described here using different locking strategies. The default level is REPEATABLE READ. For additional information about InnoDB record-level locks and how it uses them to execute various types of statements, see InnoDB Lock Modes, and http://dev.mysql.com/doc/refman/en/innodb-locks-set.html.

Isolation Levels

The following sections describe how MariaDB supports the different transaction levels.

READ UNCOMMITTED

SELECT statements are performed in a non-locking fashion, but a possible earlier version of a row might be used. Thus, using this isolation level, such reads are not consistent. This is also called a "dirty read." Otherwise, this isolation level works like READ COMMITTED.

READ COMMITTED

A somewhat Oracle-like isolation level with respect to consistent (non-locking) reads: Each consistent read, even within the same transaction, sets and reads its own fresh snapshot. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.

For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), InnoDB locks only index records, not the gaps before them, and thus allows the free insertion of new records next to locked records. For UPDATE and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition (such as WHERE id = 100), or a range-type search condition (such as WHERE id > 100). For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For range-type searches, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range. This is necessary because "phantom rows" must be blocked for MySQL replication and recovery to work.

Note: If the READ COMMITTED isolation level is used or the innodb_locks_unsafe_for_binlog system variable is enabled, there is no InnoDB gap locking except for foreign-key constraint checking and duplicate-key checking. Also, record locks for non-matching rows are released after MariaDB has evaluated the WHERE condition.If you use READ COMMITTED or enable innodb_locks_unsafe_for_binlog, you must use row-based binary logging.

REPEATABLE READ

This is the default isolation level for InnoDB. For consistent reads, there is an important difference from the READ COMMITTED isolation level: All consistent reads within the same transaction read the snapshot established by the first read. This convention means that if you issue several plain (non-locking) SELECT statements within the same transaction, these SELECT statements are consistent also with respect to each other. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.

For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), UPDATE, and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition, or a range-type search condition. For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For other search conditions, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range.

This is the minimum isolation level for non-distributed XA transactions.

SERIALIZABLE

This level is like REPEATABLE READ, but InnoDB implicitly converts all plain SELECT statements to SELECT ... LOCK IN SHARE MODE if autocommit is disabled. If autocommit is enabled, the SELECT is its own transaction. It therefore is known to be read only and can be serialized if performed as a consistent (non-locking) read and need not block for other transactions. (This means that to force a plain SELECT to block if other transactions have modified the selected rows, you should disable autocommit.)

Distributed XA transactions should always use this isolation level.

Access Mode

These clauses appeared in MariaDB 10.0.

The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables.

It is not permitted to specify both READ WRITE and READ ONLY in the same statement.

READ WRITE and READ ONLY can also be specified in the START TRANSACTION statement, in which case the specified mode is only valid for one transaction.

Examples

SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE;

Attempting to set the isolation level within an existing transaction without specifying GLOBAL or SESSION.

START TRANSACTION;

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
ERROR 1568 (25001): Transaction characteristics can't be changed while a transaction is in progress

1.1.2.7.10 SET Variable

Syntax

SET var_name = expr [, var_name = expr] ...

Description

The SET statement in stored programs is an extended version of the general SET statement. Referenced variables may be ones declared inside a stored program, global system variables, or user-defined variables.

The SET statement in stored programs is implemented as part of the pre-existing SET syntax. This allows an extended syntax of SET a=x, b=y, ... where different variable types (locally declared variables, global and session server variables, user-defined variables) can be mixed. This also allows combinations of local variables and some options that make sense only for system variables; in that case, the options are recognized but ignored.

SET can be used with both local variables and user-defined variables.

When setting several variables using the columns returned by a query, SELECT INTO should be preferred.

To set many variables to the same value, the LAST_VALUE( ) function can be used.

Below is an example of how a user-defined variable may be set:

SET @x = 1;

See Also

1.1.2.8 SHOW

1.1.2.8.1 About SHOW

SHOW has many forms that provide information about databases, tables, columns, or status information about the server. These include:

like_or_where:
    LIKE 'pattern'
  | WHERE expr

If the syntax for a given SHOW statement includes a LIKE 'pattern' part, 'pattern' is a string that can contain the SQL "%" and "_" wildcard characters. The pattern is useful for restricting statement output to matching values.

Several SHOW statements also accept a WHERE clause that provides more flexibility in specifying which rows to display. See Extended Show.

1.1.2.8.2 Extended Show

Contents

  1. Examples

The following SHOW statements can be extended by using a WHERE clause and a LIKE clause to refine the results:

As with a regular SELECT, the WHERE clause can be used for the specific columns returned, and the LIKE clause with the regular wildcards.

Examples

SHOW TABLES;
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
| t1                   |
| view1                |
+----------------------+

Showing the tables beginning with a only.

SHOW TABLES WHERE Tables_in_test LIKE 'a%';
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
+----------------------+

Variables whose name starts with aria and with a valued of greater than 8192:

SHOW VARIABLES WHERE Variable_name LIKE 'aria%' AND Value >8192;
+------------------------------+---------------------+
| Variable_name                | Value               |
+------------------------------+---------------------+
| aria_checkpoint_log_activity | 1048576             |
| aria_log_file_size           | 1073741824          |
| aria_max_sort_file_size      | 9223372036853727232 |
| aria_pagecache_buffer_size   | 134217728           |
| aria_sort_buffer_size        | 134217728           |
+------------------------------+---------------------+

Shortcut, just returning variables whose name begins with aria.

SHOW VARIABLES LIKE 'aria%';
+------------------------------------------+---------------------+
| Variable_name                            | Value               |
+------------------------------------------+---------------------+
| aria_block_size                          | 8192                |
| aria_checkpoint_interval                 | 30                  |
| aria_checkpoint_log_activity             | 1048576             |
| aria_force_start_after_recovery_failures | 0                   |
| aria_group_commit                        | none                |
| aria_group_commit_interval               | 0                   |
| aria_log_file_size                       | 1073741824          |
| aria_log_purge_type                      | immediate           |
| aria_max_sort_file_size                  | 9223372036853727232 |
| aria_page_checksum                       | ON                  |
| aria_pagecache_age_threshold             | 300                 |
| aria_pagecache_buffer_size               | 134217728           |
| aria_pagecache_division_limit            | 100                 |
| aria_recover                             | NORMAL              |
| aria_repair_threads                      | 1                   |
| aria_sort_buffer_size                    | 134217728           |
| aria_stats_method                        | nulls_unequal       |
| aria_sync_log_dir                        | NEWFILE             |
| aria_used_for_temp_tables                | ON                  |
+------------------------------------------+---------------------+

1.1.2.8.3 SHOW AUTHORS

Syntax

SHOW AUTHORS

Description

The SHOW AUTHORS statement displays information about the people who work on MariaDB. For each author, it displays Name, Location, and Comment values. All columns are encoded as latin1.

These include:

  • First the active people in MariaDB are listed.
  • Then the active people in MySQL.
  • Last the people that have contributed to MariaDB/MySQL in the past.

The order is somewhat related to importance of the contribution given to the MariaDB project, but this is not 100% accurate. There is still room for improvement and debate...

Example

SHOW AUTHORS;
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Name                           | Location                              | Comment                                                                                                                                 |
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Michael (Monty) Widenius       | Tusby, Finland                        | Lead developer and main author                                                                                                          |
| Sergei Golubchik               | Kerpen, Germany                       | Architect, Full-text search, precision math, plugin framework, merges etc                                                               |
| Igor Babaev                    | Bellevue, USA                         | Optimizer, keycache, core work                                                                                                          |
| Sergey Petrunia                | St. Petersburg, Russia                | Optimizer                                                                                                                               |
| Oleksandr Byelkin              | Lugansk, Ukraine                      | Query Cache (4.0), Subqueries (4.1), Views (5.0)                                                                                        |
| Timour Katchaounov             | Sofia , Bulgaria                      | Optimizer                                                                                                                               |
| Kristian Nielsen               | Copenhagen, Denmark                   | Replication, Async client prototocol, General buildbot stuff                                                                            |
| Alexander (Bar) Barkov         | Izhevsk, Russia                       | Unicode and character sets                                                                                                              |
| Alexey Botchkov (Holyfoot)     | Izhevsk, Russia                       | GIS extensions, embedded server, precision math                                                                                         |
| Daniel Bartholomew             | Raleigh, USA                          | MariaDB documentation                                                                                                                   |
| Colin Charles                  | Selangor, Malesia                     | MariaDB documentation, talks at a LOT of conferences                                                                                    |
| Sergey Vojtovich               | Izhevsk, Russia                       | initial implementation of plugin architecture, maintained native storage engines (MyISAM, MEMORY, ARCHIVE, etc), rewrite of table cache |
| Vladislav Vaintroub            | Mannheim, Germany                     | MariaDB Java connector, new thread pool, Windows optimizations                                                                          |
| Elena Stepanova                | Sankt Petersburg, Russia              | QA, test cases                                                                                                                          |
| Georg Richter                  | Heidelberg, Germany                   | New LGPL C connector, PHP connector                                                                                                     |
| Jan Lindström                  | Ylämylly, Finland                     | Working on InnoDB                                                                                                                       |
| Lixun Peng                     | Hangzhou, China                       | Multi Source replication                                                                                                                |
| Percona                        | CA, USA                               | XtraDB, microslow patches, extensions to slow log   
...

See Also

1.1.2.8.4 SHOW BINARY LOGS

Syntax

SHOW BINARY LOGS
SHOW MASTER LOGS

Description

Lists the binary log files on the server. This statement is used as part of the procedure described in PURGE BINARY LOGS, that shows how to determine which logs can be purged.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the BINLOG MONITOR privilege.

Examples

SHOW BINARY LOGS;
+--------------------+-----------+
| Log_name           | File_size |
+--------------------+-----------+
| mariadb-bin.000001 |     19039 |
| mariadb-bin.000002 |    717389 |
| mariadb-bin.000003 |       300 |
| mariadb-bin.000004 |       333 |
| mariadb-bin.000005 |       899 |
| mariadb-bin.000006 |       125 |
| mariadb-bin.000007 |     18907 |
| mariadb-bin.000008 |     19530 |
| mariadb-bin.000009 |       151 |
| mariadb-bin.000010 |       151 |
| mariadb-bin.000011 |       125 |
| mariadb-bin.000012 |       151 |
| mariadb-bin.000013 |       151 |
| mariadb-bin.000014 |       125 |
| mariadb-bin.000015 |       151 |
| mariadb-bin.000016 |       314 |
+--------------------+-----------+

1.1.2.8.5 SHOW BINLOG EVENTS

Syntax

SHOW BINLOG EVENTS
   [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]

Description

Shows the events in the binary log. If you do not specify 'log_name', the first binary log is displayed.

Requires the BINLOG MONITOR privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

Example

SHOW BINLOG EVENTS IN 'mysql_sandbox10019-bin.000002';
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| Log_name                      | Pos | Event_type        | Server_id | End_log_pos | Info                                           |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| mysql_sandbox10019-bin.000002 |   4 | Format_desc       |         1 |         248 | Server ver: 10.0.19-MariaDB-log, Binlog ver: 4 |
| mysql_sandbox10019-bin.000002 | 248 | Gtid_list         |         1 |         273 | []                                             |
| mysql_sandbox10019-bin.000002 | 273 | Binlog_checkpoint |         1 |         325 | mysql_sandbox10019-bin.000002                  |
| mysql_sandbox10019-bin.000002 | 325 | Gtid              |         1 |         363 | GTID 0-1-1                                     |
| mysql_sandbox10019-bin.000002 | 363 | Query             |         1 |         446 | CREATE DATABASE blog                           |
| mysql_sandbox10019-bin.000002 | 446 | Gtid              |         1 |         484 | GTID 0-1-2                                     |
| mysql_sandbox10019-bin.000002 | 484 | Query             |         1 |         571 | use `blog`; CREATE TABLE bb (id INT)           |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+

1.1.2.8.6 SHOW CHARACTER SET

Syntax

SHOW CHARACTER SET
    [LIKE 'pattern' | WHERE expr]

Description

The SHOW CHARACTER SET statement shows all available character sets. The LIKE clause, if present on its own, indicates which character set names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The same information can be queried from the Information Schema CHARACTER_SETS table.

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels.

Examples

SHOW CHARACTER SET LIKE 'latin%';
+---------+-----------------------------+-------------------+--------+
| Charset | Description                 | Default collation | Maxlen |
+---------+-----------------------------+-------------------+--------+
| latin1  | cp1252 West European        | latin1_swedish_ci |      1 |
| latin2  | ISO 8859-2 Central European | latin2_general_ci |      1 |
| latin5  | ISO 8859-9 Turkish          | latin5_turkish_ci |      1 |
| latin7  | ISO 8859-13 Baltic          | latin7_general_ci |      1 |
+---------+-----------------------------+-------------------+--------+
SHOW CHARACTER SET WHERE Maxlen LIKE '2';
+---------+---------------------------+-------------------+--------+
| Charset | Description               | Default collation | Maxlen |
+---------+---------------------------+-------------------+--------+
| big5    | Big5 Traditional Chinese  | big5_chinese_ci   |      2 |
| sjis    | Shift-JIS Japanese        | sjis_japanese_ci  |      2 |
| euckr   | EUC-KR Korean             | euckr_korean_ci   |      2 |
| gb2312  | GB2312 Simplified Chinese | gb2312_chinese_ci |      2 |
| gbk     | GBK Simplified Chinese    | gbk_chinese_ci    |      2 |
| ucs2    | UCS-2 Unicode             | ucs2_general_ci   |      2 |
| cp932   | SJIS for Windows Japanese | cp932_japanese_ci |      2 |
+---------+---------------------------+-------------------+--------+

See Also

1.1.2.8.7 SHOW CLIENT_STATISTICS

Syntax

SHOW CLIENT_STATISTICS

Description

The SHOW CLIENT_STATISTICS statement is part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.CLIENT_STATISTICS table holds statistics about client connections.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.CLIENT_STATISTICS articles for more information.

Example

SHOW CLIENT_STATISTICS\G
*************************** 1. row ***************************
                Client: localhost
     Total_connections: 35
Concurrent_connections: 0
        Connected_time: 708
             Busy_time: 2.5557979999999985
              Cpu_time: 0.04123740000000002
        Bytes_received: 3883
            Bytes_sent: 21595
  Binlog_bytes_written: 0
             Rows_read: 18
             Rows_sent: 115
          Rows_deleted: 0
         Rows_inserted: 0
          Rows_updated: 0
       Select_commands: 70
       Update_commands: 0
        Other_commands: 0
   Commit_transactions: 1
 Rollback_transactions: 0
    Denied_connections: 0
      Lost_connections: 0
         Access_denied: 0
         Empty_queries: 35

1.1.2.8.8

1.1.2.8.9 SHOW CONTRIBUTORS

Syntax

SHOW CONTRIBUTORS

Description

The SHOW CONTRIBUTORS statement displays information about the companies and people who financially contribute to MariaDB. For each contributor, it displays Name, Location, and Comment values. All columns are encoded as latin1.

It displays all members and sponsors of the MariaDB Foundation as well as other financial contributors.

Example

SHOW CONTRIBUTORS;
+---------------------+-------------------------------+-------------------------------------------------------------+
| Name                | Location                      | Comment                                                     |
+---------------------+-------------------------------+-------------------------------------------------------------+
| Booking.com         | https://www.booking.com       | Founding member, Platinum Sponsor of the MariaDB Foundation |
| Alibaba Cloud       | https://www.alibabacloud.com/ | Platinum Sponsor of the MariaDB Foundation                  |
| Tencent Cloud       | https://cloud.tencent.com     | Platinum Sponsor of the MariaDB Foundation                  |
| Microsoft           | https://microsoft.com/        | Platinum Sponsor of the MariaDB Foundation                  |
| MariaDB Corporation | https://mariadb.com           | Founding member, Platinum Sponsor of the MariaDB Foundation |
| Visma               | https://visma.com             | Gold Sponsor of the MariaDB Foundation                      |
| DBS                 | https://dbs.com               | Gold Sponsor of the MariaDB Foundation                      |
| IBM                 | https://www.ibm.com           | Gold Sponsor of the MariaDB Foundation                      |
| Tencent Games       | http://game.qq.com/           | Gold Sponsor of the MariaDB Foundation                      |
| Nexedi              | https://www.nexedi.com        | Silver Sponsor of the MariaDB Foundation                    |
| Acronis             | https://www.acronis.com       | Silver Sponsor of the MariaDB Foundation                    |
| Verkkokauppa.com    | https://www.verkkokauppa.com  | Bronze Sponsor of the MariaDB Foundation                    |
| Virtuozzo           | https://virtuozzo.com         | Bronze Sponsor of the MariaDB Foundation                    |
| Tencent Game DBA    | http://tencentdba.com/about   | Bronze Sponsor of the MariaDB Foundation                    |
| Tencent TDSQL       | http://tdsql.org              | Bronze Sponsor of the MariaDB Foundation                    |
| Percona             | https://www.percona.com/      | Bronze Sponsor of the MariaDB Foundation                    |
| Google              | USA                           | Sponsoring encryption, parallel replication and GTID        |
| Facebook            | USA                           | Sponsoring non-blocking API, LIMIT ROWS EXAMINED etc        |
| Ronald Bradford     | Brisbane, Australia           | EFF contribution for UC2006 Auction                         |
| Sheeri Kritzer      | Boston, Mass. USA             | EFF contribution for UC2006 Auction                         |
| Mark Shuttleworth   | London, UK.                   | EFF contribution for UC2006 Auction                         |
+---------------------+-------------------------------+-------------------------------------------------------------+

See Also

1.1.2.8.10 SHOW CREATE DATABASE

Syntax

SHOW CREATE {DATABASE | SCHEMA} db_name

Description

Shows the CREATE DATABASE statement that creates the given database. SHOW CREATE SCHEMA is a synonym for SHOW CREATE DATABASE. SHOW CREATE DATABASE quotes database names according to the value of the sql_quote_show_create server system variable.

Examples

SHOW CREATE DATABASE test;
+----------+-----------------------------------------------------------------+
| Database | Create Database                                                 |
+----------+-----------------------------------------------------------------+
| test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+

SHOW CREATE SCHEMA test;
+----------+-----------------------------------------------------------------+
| Database | Create Database                                                 |
+----------+-----------------------------------------------------------------+
| test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+

With sql_quote_show_create off:

SHOW CREATE DATABASE test;
+----------+---------------------------------------------------------------+
| Database | Create Database                                               |
+----------+---------------------------------------------------------------+
| test     | CREATE DATABASE test /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+---------------------------------------------------------------+

With a comment, from MariaDB 10.5:

SHOW CREATE DATABASE p;
+----------+--------------------------------------------------------------------------------------+
| Database | Create Database                                                                      |
+----------+--------------------------------------------------------------------------------------+
| p        | CREATE DATABASE `p` /*!40100 DEFAULT CHARACTER SET latin1 */ COMMENT 'presentations' |
+----------+--------------------------------------------------------------------------------------+

See Also

1.1.2.8.11 SHOW CREATE EVENT

Syntax

SHOW CREATE EVENT event_name

Description

This statement displays the CREATE EVENT statement needed to re-create a given event, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection. To find out which events are present, use SHOW EVENTS.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

The information_schema.EVENTS table provides similar, but more complete, information.

Examples

SHOW CREATE EVENT test.e_daily\G
*************************** 1. row ***************************
               Event: e_daily
            sql_mode: 
           time_zone: SYSTEM
        Create Event: CREATE EVENT `e_daily`
                        ON SCHEDULE EVERY 1 DAY
                        STARTS CURRENT_TIMESTAMP + INTERVAL 6 HOUR
                        ON COMPLETION NOT PRESERVE
                        ENABLE
                        COMMENT 'Saves total number of sessions then
                                clears the table each day'
                        DO BEGIN
                          INSERT INTO site_activity.totals (time, total)
                            SELECT CURRENT_TIMESTAMP, COUNT(*) 
                            FROM site_activity.sessions;
                          DELETE FROM site_activity.sessions;
                        END
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

See also

1.1.2.8.12 SHOW CREATE FUNCTION

Syntax

SHOW CREATE FUNCTION func_name

Description

This statement is similar to SHOW CREATE PROCEDURE but for stored functions.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Example

MariaDB [test]> SHOW CREATE FUNCTION VatCents\G
*************************** 1. row ***************************
            Function: VatCents
            sql_mode: 
     Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `VatCents`(price DECIMAL(10,2)) RETURNS int(11)
    DETERMINISTIC
BEGIN
 DECLARE x INT;
 SET x = price * 114;
 RETURN x;
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See also:

1.1.2.8.13 SHOW CREATE PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW CREATE PACKAGE  [ db_name . ] package_name

Description

The SHOW CREATE PACKAGE statement can be used when Oracle SQL_MODE is set.

Shows the CREATE statement that creates the given package specification.

Examples

SHOW CREATE PACKAGE employee_tools\G
*************************** 1. row ***************************
             Package: employee_tools
            sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
      Create Package: CREATE DEFINER="root"@"localhost" PACKAGE "employee_tools" AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.2.8.14 SHOW CREATE PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW CREATE PACKAGE BODY  [ db_name . ] package_name

Description

The SHOW CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

Shows the CREATE statement that creates the given package body (i.e. the implementation).

Examples

SHOW CREATE PACKAGE BODY employee_tools\G
*************************** 1. row ***************************
        Package body: employee_tools
            sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
 Create Package Body: CREATE DEFINER="root"@"localhost" PACKAGE BODY "employee_tools" AS
  
  stdRaiseAmount DECIMAL(10,2):=500;
  
  PROCEDURE log (eid INT, ecmnt TEXT) AS
  BEGIN
    INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
  END;
  
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
    eid INT;
  BEGIN
    INSERT INTO employee (name, salary) VALUES (ename, esalary);
    eid:= last_insert_id();
    log(eid, 'hire ' || ename);
  END;

  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
    nSalary DECIMAL(10,2);
  BEGIN
    SELECT salary INTO nSalary FROM employee WHERE id=eid;
    log(eid, 'getSalary id=' || eid || ' salary=' || nSalary);
    RETURN nSalary;
  END;

  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
  BEGIN
    UPDATE employee SET salary=salary+amount WHERE id=eid;
    log(eid, 'raiseSalary id=' || eid || ' amount=' || amount);
  END;

  PROCEDURE raiseSalaryStd(eid INT) AS
  BEGIN
    raiseSalary(eid, stdRaiseAmount);
    log(eid, 'raiseSalaryStd id=' || eid);
  END;

BEGIN  
  log(0, 'Session ' || connection_id() || ' ' || current_user || ' started');
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See also

1.1.2.8.15 SHOW CREATE PROCEDURE

Syntax

SHOW CREATE PROCEDURE proc_name

Description

This statement is a MariaDB extension. It returns the exact string that can be used to re-create the named stored procedure, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.. A similar statement, SHOW CREATE FUNCTION, displays information about stored functions.

Both statements require that you are the owner of the routine or have the SELECT privilege on the mysql.proc table. When neither is true, the statements display NULL for the Create Procedure or Create Function field.

Warning Users with SELECT privileges on mysql.proc or USAGE privileges on *.* can view the text of routines, even when they do not have privileges for the function or procedure itself.

The output of these statements is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Examples

Here's a comparison of the SHOW CREATE PROCEDURE and SHOW CREATE FUNCTION statements.

SHOW CREATE PROCEDURE test.simpleproc\G
*************************** 1. row ***************************
           Procedure: simpleproc
            sql_mode: 
    Create Procedure: CREATE PROCEDURE `simpleproc`(OUT param1 INT)
                      BEGIN
                      SELECT COUNT(*) INTO param1 FROM t;
                      END
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

SHOW CREATE FUNCTION test.hello\G
*************************** 1. row ***************************
            Function: hello
            sql_mode:
     Create Function: CREATE FUNCTION `hello`(s CHAR(20))
                      RETURNS CHAR(50)
                      RETURN CONCAT('Hello, ',s,'!')
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

When the user issuing the statement does not have privileges on the routine, attempting to CALL the procedure raises Error 1370.

CALL test.prc1();
Error 1370 (42000): execute command denieed to user 'test_user'@'localhost' for routine 'test'.'prc1'

If the user neither has privilege to the routine nor the SELECT privilege on mysql.proc table, it raises Error 1305, informing them that the procedure does not exist.

SHOW CREATE TABLES test.prc1\G
Error 1305 (42000): PROCEDURE prc1 does not exist

See Also

1.1.2.8.16 SHOW CREATE SEQUENCE

MariaDB starting with 10.3.1

Sequences were introduced in MariaDB 10.3.

Syntax

SHOW CREATE SEQUENCE sequence_name;

Description

Shows the CREATE SEQUENCE statement that created the given sequence. The statement requires the SELECT privilege for the table.

Example

CREATE SEQUENCE s1 START WITH 50;
SHOW CREATE SEQUENCE s1\G;
*************************** 1. row ***************************
       Table: s1
Create Table: CREATE SEQUENCE `s1` start with 50 minvalue 1 maxvalue 9223372036854775806 
  increment by 1 cache 1000 nocycle ENGINE=InnoDB

Notes

If you want to see the underlying table structure used for the SEQUENCE you can use SHOW CREATE TABLE on the SEQUENCE. You can also use SELECT to read the current recorded state of the SEQUENCE:

SHOW CREATE TABLE s1\G
*************************** 1. row ***************************
       Table: s1
Create Table: CREATE TABLE `s1` (
  `next_not_cached_value` bigint(21) NOT NULL,
  `minimum_value` bigint(21) NOT NULL,
  `maximum_value` bigint(21) NOT NULL,
  `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created 
     or value if RESTART is used',
  `increment` bigint(21) NOT NULL COMMENT 'increment value',
  `cache_size` bigint(21) unsigned NOT NULL,
  `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 
     1 if the sequence should begin a new cycle when maximum_value is passed',
  `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
) ENGINE=InnoDB SEQUENCE=1

SELECT * FROM s1\G
*************************** 1. row ***************************
next_not_cached_value: 50
        minimum_value: 1
        maximum_value: 9223372036854775806
          start_value: 50
            increment: 1
           cache_size: 1000
         cycle_option: 0
          cycle_count: 0

See Also

1.1.2.8.17

1.1.2.8.18 SHOW CREATE TRIGGER

Syntax

SHOW CREATE TRIGGER trigger_name

Description

This statement shows a CREATE TRIGGER statement that creates the given trigger, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Examples

SHOW CREATE TRIGGER example\G
*************************** 1. row ***************************
               Trigger: example
              sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,STRICT_ALL_TABLES
,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_
ENGINE_SUBSTITUTION
SQL Original Statement: CREATE DEFINER=`root`@`localhost` TRIGGER example BEFORE
 INSERT ON t FOR EACH ROW
BEGIN
        SET NEW.c = NEW.c * 2;
END
  character_set_client: cp850
  collation_connection: cp850_general_ci
  Database Collation: utf8_general_ci
  Created: 2016-09-29 13:53:34.35
MariaDB starting with 10.2.3

The Created column was added in MySQL 5.7 and MariaDB 10.2.3 as part of introducing multiple trigger events per action.

See also

1.1.2.8.19

1.1.2.8.20 SHOW CREATE VIEW

Syntax

SHOW CREATE VIEW view_name

Description

This statement shows a CREATE VIEW statement that creates the given view, as well as the character set used by the connection when the view was created. This statement also works with views.

SHOW CREATE VIEW quotes table, column and stored function names according to the value of the sql_quote_show_create server system variable.

Examples

SHOW CREATE VIEW example\G
*************************** 1. row ***************************
                View: example
         Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL
SECURITY DEFINER VIEW `example` AS (select `t`.`id` AS `id`,`t`.`s` AS `s` from
`t`)
character_set_client: cp850
collation_connection: cp850_general_ci

With sql_quote_show_create off:

SHOW CREATE VIEW example\G
*************************** 1. row ***************************
                View: example
         Create View: CREATE ALGORITHM=UNDEFINED DEFINER=root@localhost SQL SECU
RITY DEFINER VIEW example AS (select t.id AS id,t.s AS s from t)
character_set_client: cp850
collation_connection: cp850_general_ci

1.1.2.8.21 SHOW DATABASES

Syntax

SHOW {DATABASES | SCHEMAS}
    [LIKE 'pattern' | WHERE expr]

Description

SHOW DATABASES lists the databases on the MariaDB server host. SHOW SCHEMAS is a synonym for SHOW DATABASES. The LIKE clause, if present on its own, indicates which database names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

You see only those databases for which you have some kind of privilege, unless you have the global SHOW DATABASES privilege. You can also get this list using the mysqlshow command.

If the server was started with the --skip-show-database option, you cannot use this statement at all unless you have the SHOW DATABASES privilege.

The list of results returned by SHOW DATABASES is based on directories in the data directory, which is how MariaDB implements databases. It's possible that output includes directories that do not correspond to actual databases.

The Information Schema SCHEMATA table also contains database information.

Examples

SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
SHOW DATABASES LIKE 'm%';
+---------------+
| Database (m%) |
+---------------+
| mysql         |
+---------------+

See Also

1.1.2.8.22 SHOW ENGINE

Syntax

SHOW ENGINE engine_name {STATUS | MUTEX}

Description

SHOW ENGINE displays operational information about a storage engine. The following statements currently are supported:

SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB MUTEX
SHOW ENGINE PERFORMANCE_SCHEMA STATUS
SHOW ENGINE ROCKSDB STATUS

If the Sphinx Storage Engine is installed, the following is also supported:

SHOW ENGINE SPHINX STATUS

See SHOW ENGINE SPHINX STATUS.

Older (and now removed) synonyms were SHOW INNODB STATUS for SHOW ENGINE INNODB STATUS and SHOW MUTEX STATUS for SHOW ENGINE INNODB MUTEX.

SHOW ENGINE INNODB STATUS

SHOW ENGINE INNODB STATUS displays extensive information from the standard InnoDB Monitor about the state of the InnoDB storage engine. See SHOW ENGINE INNODB STATUS for more.

SHOW ENGINE INNODB MUTEX

SHOW ENGINE INNODB MUTEX displays InnoDB mutex statistics.

The statement displays the following output fields:

  • Type: Always InnoDB.
  • Name: The source file where the mutex is implemented, and the line number in the file where the mutex is created. The line number is dependent on the MariaDB version.
  • Status: This field displays the following values if UNIV_DEBUG was defined at compilation time (for example, in include/univ.h in the InnoDB part of the source tree). Only the os_waits value is displayed if UNIV_DEBUG was not defined. Without UNIV_DEBUG, the information on which the output is based is insufficient to distinguish regular mutexes and mutexes that protect rw-locks (which allow multiple readers or a single writer). Consequently, the output may appear to contain multiple rows for the same mutex.
    • count indicates how many times the mutex was requested.
    • spin_waits indicates how many times the spinlock had to run.
    • spin_rounds indicates the number of spinlock rounds. (spin_rounds divided by spin_waits provides the average round count.)
    • os_waits indicates the number of operating system waits. This occurs when the spinlock did not work (the mutex was not locked during the spinlock and it was necessary to yield to the operating system and wait).
    • os_yields indicates the number of times a the thread trying to lock a mutex gave up its timeslice and yielded to the operating system (on the presumption that allowing other threads to run will free the mutex so that it can be locked).
    • os_wait_times indicates the amount of time (in ms) spent in operating system waits, if the timed_mutexes system variable is 1 (ON). If timed_mutexes is 0 (OFF), timing is disabled, so os_wait_times is 0. timed_mutexes is off by default.

Information from this statement can be used to diagnose system problems. For example, large values of spin_waits and spin_rounds may indicate scalability problems.

The information_schema.INNODB_MUTEXES table provides similar information.

SHOW ENGINE PERFORMANCE_SCHEMA STATUS

This statement shows how much memory is used for performance_schema tables and internal buffers.

The output contains the following fields:

  • Type: Always performance_schema.
  • Name: The name of a table, the name of an internal buffer, or the performance_schema word, followed by a dot and an attribute. Internal buffers names are enclosed by parenthesis. performance_schema means that the attribute refers to the whole database (it is a total).
  • Status: The value for the attribute.

The following attributes are shown, in this order, for all tables:

  • row_size: The memory used for an individual record. This value will never change.
  • row_count: The number of rows in the table or buffer. For some tables, this value depends on a server system variable.
  • memory: For tables and performance_schema, this is the result of row_size * row_count.

For internal buffers, the attributes are:

  • count
  • size

SHOW ENGINE ROCKSDB STATUS

See also MyRocks Performance Troubleshooting

1.1.2.8.23 SHOW ENGINE INNODB STATUS

SHOW ENGINE INNODB STATUS is a specific form of the SHOW ENGINE statement that displays the InnoDB Monitor output, which is extensive InnoDB information which can be useful in diagnosing problems.

The following sections are displayed

  • Status: Shows the timestamp, monitor name and the number of seconds, or the elapsed time between the current time and the time the InnoDB Monitor output was last displayed. The per-second averages are based upon this time.
  • BACKGROUND THREAD: srv_master_thread lines show work performed by the main background thread.
  • SEMAPHORES: Threads waiting for a semaphore and stats on how the number of times threads have needed a spin or a wait on a mutex or rw-lock semaphore. If this number of threads is large, there may be I/O or contention issues. Reducing the size of the innodb_thread_concurrency system variable may help if contention is related to thread scheduling. Spin rounds per wait shows the number of spinlock rounds per OS wait for a mutex.
  • LATEST FOREIGN KEY ERROR: Only shown if there has been a foreign key constraint error, it displays the failed statement and information about the constraint and the related tables.
  • LATEST DETECTED DEADLOCK: Only shown if there has been a deadlock, it displays the transactions involved in the deadlock and the statements being executed, held and required locked and the transaction rolled back to.
  • TRANSACTIONS: The output of this section can help identify lock contention, as well as reasons for the deadlocks.
  • FILE I/O: InnoDB thread information as well as pending I/O operations and I/O performance statistics.
  • INSERT BUFFER AND ADAPTIVE HASH INDEX: InnoDB insert buffer (old name for the change buffer) and adaptive hash index status information, including the number of each type of operation performed, and adaptive hash index performance.
  • LOG: InnoDB log information, including current log sequence number, how far the log has been flushed to disk, the position at which InnoDB last took a checkpoint, pending writes and write performance statistics.
  • BUFFER POOL AND MEMORY: Information on buffer pool pages read and written, which allows you to see the number of data file I/O operations performed by your queries. See InnoDB Buffer Pool for more. Similar information is also available from the INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS table.
  • ROW OPERATIONS:Information about the main thread, including the number and performance rate for each type of row operation.

If the innodb_status_output_locks system variable is set to 1, extended lock information will be displayed.

Example output:

=====================================
2019-09-06 12:44:13 0x7f93cc236700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 4 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 2 srv_active, 0 srv_shutdown, 83698 srv_idle
srv_master_thread log flush and writes: 83682
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 15
OS WAIT ARRAY INFO: signal count 8
RW-shared spins 0, rounds 20, OS waits 7
RW-excl spins 0, rounds 0, OS waits 0
RW-sx spins 0, rounds 0, OS waits 0
Spin rounds per wait: 20.00 RW-shared, 0.00 RW-excl, 0.00 RW-sx
------------
TRANSACTIONS
------------
Trx id counter 236
Purge done for trx's n:o < 236 undo n:o < 0 state: running
History list length 22
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421747401994584, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421747401990328, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
 ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 0
286 OS file reads, 171 OS file writes, 22 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 0 merges
merged operations:
 insert 0, delete mark 0, delete 0
discarded operations:
 insert 0, delete mark 0, delete 0
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 445926
Log flushed up to   445926
Pages flushed up to 445926
Last checkpoint at  445917
0 pending log flushes, 0 pending chkp writes
18 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 167772160
Dictionary memory allocated 50768
Buffer pool size   8012
Free buffers       7611
Database pages     401
Old database pages 0
Modified db pages  0
Percent of dirty pages(LRU & free pages): 0.000
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 264, created 137, written 156
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 401, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Process ID=4267, Main thread ID=140272021272320, state: sleeping
Number of rows inserted 1, updated 0, deleted 0, read 1
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read 0
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================

1.1.2.8.24 SHOW ENGINES

Syntax

SHOW [STORAGE] ENGINES

Description

SHOW ENGINES displays status information about the server's storage engines. This is particularly useful for checking whether a storage engine is supported, or to see what the default engine is. SHOW TABLE TYPES is a deprecated synonym.

The information_schema.ENGINES table provides the same information.

Since storage engines are plugins, different information about them is also shown in the information_schema.PLUGINS table and by the SHOW PLUGINS statement.

Note that both MySQL's InnoDB and Percona's XtraDB replacement are labeled as InnoDB. However, if XtraDB is in use, it will be specified in the COMMENT field. See XtraDB and InnoDB. The same applies to FederatedX.

The output consists of the following columns:

  • Engine indicates the engine's name.
  • Support indicates whether the engine is installed, and whether it is the default engine for the current session.
  • Comment is a brief description.
  • Transactions, XA and Savepoints indicate whether transactions, XA transactions and transaction savepoints are supported by the engine.

Examples

SHOW ENGINES\G
*************************** 1. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 2. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: FEDERATED
     Support: YES
     Comment: FederatedX pluggable storage engine
Transactions: YES
          XA: NO
  Savepoints: YES
*************************** 6. row ***************************
      Engine: MRG_MyISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 10. row ***************************
      Engine: Aria
     Support: YES
     Comment: Crash-safe tables with MyISAM heritage
Transactions: NO
          XA: NO
  Savepoints: NO
10 rows in set (0.00 sec)

1.1.2.8.25 SHOW ERRORS

Syntax

SHOW ERRORS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) ERRORS

Description

This statement is similar to SHOW WARNINGS, except that instead of displaying errors, warnings, and notes, it displays only errors.

The LIMIT clause has the same syntax as for the SELECT statement.

The SHOW COUNT(*) ERRORS statement displays the number of errors. You can also retrieve this number from the error_count variable.

SHOW COUNT(*) ERRORS;
SELECT @@error_count;

The value of error_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored.

For a list of MariaDB error codes, see MariaDB Error Codes.

Examples

SELECT f();
ERROR 1305 (42000): FUNCTION f does not exist

SHOW COUNT(*) ERRORS;
+-----------------------+
| @@session.error_count |
+-----------------------+
|                     1 |
+-----------------------+

SHOW ERRORS;
+-------+------+---------------------------+
| Level | Code | Message                   |
+-------+------+---------------------------+
| Error | 1305 | FUNCTION f does not exist |
+-------+------+---------------------------+

1.1.2.8.26 SHOW EVENTS

Syntax

SHOW EVENTS [{FROM | IN} schema_name]
    [LIKE 'pattern' | WHERE expr]

Description

Shows information about Event Manager events (created with CREATE EVENT). Requires the EVENT privilege. Without any arguments, SHOW EVENTS lists all of the events in the current schema:

SELECT CURRENT_USER(), SCHEMA();
+----------------+----------+
| CURRENT_USER() | SCHEMA() |
+----------------+----------+
| jon@ghidora    | myschema |
+----------------+----------+

SHOW EVENTS\G
*************************** 1. row ***************************
                  Db: myschema
                Name: e_daily
             Definer: jon@ghidora
           Time zone: SYSTEM
                Type: RECURRING
          Execute at: NULL
      Interval value: 10
      Interval field: SECOND
              Starts: 2006-02-09 10:41:23
                Ends: NULL
              Status: ENABLED
          Originator: 0
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

To see the event action, use SHOW CREATE EVENT instead, or look at the information_schema.EVENTS table.

To see events for a specific schema, use the FROM clause. For example, to see events for the test schema, use the following statement:

SHOW EVENTS FROM test;

The LIKE clause, if present, indicates which event names to match. The WHERE clause can be given to select rows using more general conditions, as discussed in Extended Show.

1.1.2.8.27 SHOW FUNCTION STATUS

Syntax

SHOW FUNCTION STATUS
    [LIKE 'pattern' | WHERE expr]

Description

This statement is similar to SHOW PROCEDURE STATUS but for stored functions.

The LIKE clause, if present on its own, indicates which function names to match.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The information_schema.ROUTINES table contains more detailed information.

Examples

Showing all stored functions:

SHOW FUNCTION STATUS\G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Stored functions whose name starts with 'V':

SHOW FUNCTION STATUS LIKE 'V%' \G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Stored functions with a security type of 'DEFINER':

SHOW FUNCTION STATUS WHERE Security_type LIKE 'DEFINER' \G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

1.1.2.8.28

1.1.2.8.29

1.1.2.8.30 SHOW INDEX_STATISTICS

Syntax

SHOW INDEX_STATISTICS

Description

The SHOW INDEX_STATISTICS statement was introduced in MariaDB 5.2 as part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schmea.INDEX_STATISTICS table shows statistics on index usage and makes it possible to do such things as locating unused indexes and generating the commands to remove them.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.INDEX_STATISTICS table for more information.

Example

SHOW INDEX_STATISTICS;
+--------------+-------------------+------------+-----------+
| Table_schema | Table_name        | Index_name | Rows_read |
+--------------+-------------------+------------+-----------+
| test         | employees_example | PRIMARY    |         1 |
+--------------+-------------------+------------+-----------+

1.1.2.8.32 SHOW LOCALES

SHOW LOCALES was introduced as part of the Information Schema plugin extension.

SHOW LOCALES is used to return locales information as part of the Locales plugin. While the information_schema.LOCALES table has 8 columns, the SHOW LOCALES statement will only display 4 of them:

Example

SHOW LOCALES;
+-----+-------+-------------------------------------+------------------------+
| Id  | Name  | Description                         | Error_Message_Language |
+-----+-------+-------------------------------------+------------------------+
|   0 | en_US | English - United States             | english                |
|   1 | en_GB | English - United Kingdom            | english                |
|   2 | ja_JP | Japanese - Japan                    | japanese               |
|   3 | sv_SE | Swedish - Sweden                    | swedish                |
...

1.1.2.8.33

1.1.2.8.34 SHOW OPEN TABLES

Syntax

SHOW OPEN TABLES [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW OPEN TABLES lists the non-TEMPORARY tables that are currently open in the table cache. See http://dev.mysql.com/doc/refman/5.1/en/table-cache.html.

The FROM and LIKE clauses may be used.

The FROM clause, if present, restricts the tables shown to those present in the db_name database.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The following information is returned:

ColumnDescription
DatabaseDatabase name.
NameTable name.
In_useNumber of table instances being used.
Name_locked1 if the table is name-locked, e.g. if it is being dropped or renamed, otherwise 0.

Before MariaDB 5.5, each use of, for example, LOCK TABLE ... WRITE would increment In_use for that table. With the implementation of the metadata locking improvements in MariaDB 5.5, LOCK TABLE... WRITE acquires a strong MDL lock, and concurrent connections will wait on this MDL lock, so any subsequent LOCK TABLE... WRITE will not increment In_use.

Example

SHOW OPEN TABLES;
+----------+---------------------------+--------+-------------+
| Database | Table                     | In_use | Name_locked |
+----------+---------------------------+--------+-------------+
...
| test     | xjson                     |      0 |           0 |
| test     | jauthor                   |      0 |           0 |
| test     | locks                     |      1 |           0 |
...
+----------+---------------------------+--------+-------------+

1.1.2.8.35 SHOW PACKAGE BODY STATUS

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW PACKAGE BODY STATUS
    [LIKE 'pattern' | WHERE expr]

Description

The SHOW PACKAGE BODY STATUS statement returns characteristics of stored package bodies (implementations), such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE STATUS, displays information about stored package specifications.

The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PACKAGE BODY STATUS LIKE 'pkg1'\G
*************************** 1. row ***************************
                  Db: test
                Name: pkg1
                Type: PACKAGE BODY
             Definer: root@localhost
            Modified: 2018-02-27 14:44:14
             Created: 2018-02-27 14:44:14
       Security_type: DEFINER
             Comment: This is my first package body
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.2.8.36 SHOW PACKAGE STATUS

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW PACKAGE STATUS
    [LIKE 'pattern' | WHERE expr]

Description

The SHOW PACKAGE STATUS statement returns characteristics of stored package specifications, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE BODY STATUS, displays information about stored package bodies (i.e. implementations).

The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PACKAGE STATUS LIKE 'pkg1'\G
*************************** 1. row ***************************
                  Db: test
                Name: pkg1
                Type: PACKAGE
             Definer: root@localhost
            Modified: 2018-02-27 14:38:15
             Created: 2018-02-27 14:38:15
       Security_type: DEFINER
             Comment: This is my first package
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.2.8.37

1.1.2.8.38

1.1.2.8.39 SHOW PRIVILEGES

Syntax

SHOW PRIVILEGES

Description

SHOW PRIVILEGES shows the list of system privileges that the MariaDB server supports. The exact list of privileges depends on the version of your server.

Note that before MariaDB 10.3.23, MariaDB 10.4.13 and MariaDB 10.5.2 , the Delete history privilege displays as Delete versioning rows (MDEV-20382).

Example

From MariaDB 10.5.9

SHOW PRIVILEGES;
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
| Privilege                | Context                               | Comment                                                            |
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
| Alter                    | Tables                                | To alter the table                                                 |
| Alter routine            | Functions,Procedures                  | To alter or drop stored functions/procedures                       |
| Create                   | Databases,Tables,Indexes              | To create new databases and tables                                 |
| Create routine           | Databases                             | To use CREATE FUNCTION/PROCEDURE                                   |
| Create temporary tables  | Databases                             | To use CREATE TEMPORARY TABLE                                      |
| Create view              | Tables                                | To create new views                                                |
| Create user              | Server Admin                          | To create new users                                                |
| Delete                   | Tables                                | To delete existing rows                                            |
| Delete history           | Tables                                | To delete versioning table historical rows                         |
| Drop                     | Databases,Tables                      | To drop databases, tables, and views                               |
| Event                    | Server Admin                          | To create, alter, drop and execute events                          |
| Execute                  | Functions,Procedures                  | To execute stored routines                                         |
| File                     | File access on server                 | To read and write files on the server                              |
| Grant option             | Databases,Tables,Functions,Procedures | To give to other users those privileges you possess                |
| Index                    | Tables                                | To create or drop indexes                                          |
| Insert                   | Tables                                | To insert data into tables                                         |
| Lock tables              | Databases                             | To use LOCK TABLES (together with SELECT privilege)                |
| Process                  | Server Admin                          | To view the plain text of currently executing queries              |
| Proxy                    | Server Admin                          | To make proxy user possible                                        |
| References               | Databases,Tables                      | To have references on tables                                       |
| Reload                   | Server Admin                          | To reload or refresh tables, logs and privileges                   |
| Binlog admin             | Server                                | To purge binary logs                                               |
| Binlog monitor           | Server                                | To use SHOW BINLOG STATUS and SHOW BINARY LOG                      |
| Binlog replay            | Server                                | To use BINLOG (generated by mariadb-binlog)                        |
| Replication master admin | Server                                | To monitor connected slaves                                        |
| Replication slave admin  | Server                                | To start/stop slave and apply binlog events                        |
| Slave monitor            | Server                                | To use SHOW SLAVE STATUS and SHOW RELAYLOG EVENTS                  |
| Replication slave        | Server Admin                          | To read binary log events from the master                          |
| Select                   | Tables                                | To retrieve rows from table                                        |
| Show databases           | Server Admin                          | To see all databases with SHOW DATABASES                           |
| Show view                | Tables                                | To see views with SHOW CREATE VIEW                                 |
| Shutdown                 | Server Admin                          | To shut down the server                                            |
| Super                    | Server Admin                          | To use KILL thread, SET GLOBAL, CHANGE MASTER, etc.                |
| Trigger                  | Tables                                | To use triggers                                                    |
| Create tablespace        | Server Admin                          | To create/alter/drop tablespaces                                   |
| Update                   | Tables                                | To update existing rows                                            |
| Set user                 | Server                                | To create views and stored routines with a different definer       |
| Federated admin          | Server                                | To execute the CREATE SERVER, ALTER SERVER, DROP SERVER statements |
| Connection admin         | Server                                | To bypass connection limits and kill other users' connections      |
| Read_only admin          | Server                                | To perform write operations even if @@read_only=ON                 |
| Usage                    | Server Admin                          | No privileges - allow connect only                                 |
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
41 rows in set (0.000 sec)

See Also

1.1.2.8.40 SHOW PROCEDURE CODE

Syntax

SHOW PROCEDURE CODE proc_name

Description

This statement is a MariaDB extension that is available only for servers that have been built with debugging support. It displays a representation of the internal implementation of the named stored procedure. A similar statement, SHOW FUNCTION CODE, displays information about stored functions.

Both statements require that you be the owner of the routine or have SELECT access to the mysql.proc table.

If the named routine is available, each statement produces a result set. Each row in the result set corresponds to one "instruction" in the routine. The first column is Pos, which is an ordinal number beginning with 0. The second column is Instruction, which contains an SQL statement (usually changed from the original source), or a directive which has meaning only to the stored-routine handler.

Examples

DELIMITER //

CREATE PROCEDURE p1 ()
  BEGIN
    DECLARE fanta INT DEFAULT 55;
    DROP TABLE t2;
    LOOP
      INSERT INTO t3 VALUES (fanta);
      END LOOP;
  END//
Query OK, 0 rows affected (0.00 sec)

SHOW PROCEDURE CODE p1//
+-----+----------------------------------------+
| Pos | Instruction                            |
+-----+----------------------------------------+
|   0 | set fanta@0 55                         |
|   1 | stmt 9 "DROP TABLE t2"                 |
|   2 | stmt 5 "INSERT INTO t3 VALUES (fanta)" |
|   3 | jump 2                                 |
+-----+----------------------------------------+

See Also

1.1.2.8.41 SHOW PROCEDURE STATUS

Syntax

SHOW PROCEDURE STATUS
    [LIKE 'pattern' | WHERE expr]

Description

This statement is a MariaDB extension. It returns characteristics of a stored procedure, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW FUNCTION STATUS, displays information about stored functions.

The LIKE clause, if present, indicates which procedure or function names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PROCEDURE STATUS LIKE 'p1'\G
*************************** 1. row ***************************
                  Db: test
                Name: p1
                Type: PROCEDURE
             Definer: root@localhost
            Modified: 2010-08-23 13:23:03
             Created: 2010-08-23 13:23:03
       Security_type: DEFINER
             Comment: 
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.2.8.42 SHOW PROCESSLIST

Syntax

SHOW [FULL] PROCESSLIST

Description

SHOW PROCESSLIST shows you which threads are running. You can also get this information from the information_schema.PROCESSLIST table or the mysqladmin processlist command. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using). If you do not use the FULL keyword, only the first 100 characters of each statement are shown in the Info field.

The columns shown in SHOW PROCESSLIST are:

NameDescription
IDThe client's process ID.
USERThe username associated with the process.
HOSTThe host the client is connected to.
DBThe default database of the process (NULL if no default).
COMMANDThe command type. See Thread Command Values.
TIMEThe amount of time, in seconds, the process has been in its current state. For a replica SQL thread before MariaDB 10.1, this is the time in seconds between the last replicated event's timestamp and the replica machine's real time.
STATESee Thread States.
INFOThe statement being executed.
PROGRESSThe total progress of the process (0-100%) (see Progress Reporting).

See TIME_MS column in information_schema.PROCESSLIST for differences in the TIME column between MariaDB and MySQL.

The information_schema.PROCESSLIST table contains the following additional columns:

NameDescription
TIME_MSThe amount of time, in milliseconds, the process has been in its current state.
STAGEThe stage the process is currently in.
MAX_STAGEThe maximum number of stages.
PROGRESSThe progress of the process within the current stage (0-100%).
MEMORY_USEDThe amount of memory used by the process.
EXAMINED_ROWSThe number of rows the process has examined.
QUERY_IDQuery ID.

Note that the PROGRESS field from the information schema, and the PROGRESS field from SHOW PROCESSLIST display different results. SHOW PROCESSLIST shows the total progress, while the information schema shows the progress for the current stage only.

Threads can be killed using their thread_id, or, since MariaDB 10.0.5, their query_id, with the KILL statement.

Since queries on this table are locking, if the performance_schema is enabled, you may want to query the THREADS table instead.

Examples

SHOW PROCESSLIST;
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
| Id | User            | Host      | db   | Command | Time | State                  | Info             | Progress |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
|  2 | event_scheduler | localhost | NULL | Daemon  | 2693 | Waiting on empty queue | NULL             |    0.000 |
|  4 | root            | localhost | NULL | Query   |    0 | Table lock             | SHOW PROCESSLIST |    0.000 |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+

See also

CONNECTION_ID()

1.1.2.8.43 SHOW PROFILES

Syntax

SHOW PROFILES

Description

The SHOW PROFILES statement displays profiling information that indicates resource usage for statements executed during the course of the current session. It is used together with SHOW PROFILE.

1.1.2.8.44 SHOW QUERY_RESPONSE_TIME

It is possible to use SHOW QUERY_RESPONSE_TIME as an alternative for retrieving information from the QUERY_RESPONSE_TIME plugin.

This was introduced as part of the Information Schema plugin extension.

1.1.2.8.45

1.1.2.8.46

1.1.2.8.47

1.1.2.8.48 SHOW STATUS

Syntax

SHOW [GLOBAL | SESSION] STATUS
    [LIKE 'pattern' | WHERE expr]

Description

SHOW STATUS provides server status information. This information also can be obtained using the mysqladmin extended-status command, or by querying the Information Schema GLOBAL_STATUS and SESSION_STATUS tables. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions.

With the GLOBAL modifier, SHOW STATUS displays the status values for all connections to MariaDB. With SESSION, it displays the status values for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. If you see a lot of 0 values, the reason is probably that you have used SHOW STATUS with a new connection instead of SHOW GLOBAL STATUS.

Some status variables have only a global value. For these, you get the same value for both GLOBAL and SESSION.

See Server Status Variables for a full list, scope and description of the variables that can be viewed with SHOW STATUS.

The LIKE clause, if present on its own, indicates which variable name to match.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Examples

Full output from MariaDB 10.1.17:

SHOW GLOBAL STATUS;
+--------------------------------------------------------------+----------------------------------------+
| Variable_name                                                | Value                                  |
+--------------------------------------------------------------+----------------------------------------+
| Aborted_clients                                              | 0                                      |
| Aborted_connects                                             | 0                                      |
| Access_denied_errors                                         | 0                                      |
| Acl_column_grants                                            | 0                                      |
| Acl_database_grants                                          | 2                                      |
| Acl_function_grants                                          | 0                                      |
| Acl_procedure_grants                                         | 0                                      |
| Acl_proxy_users                                              | 2                                      |
| Acl_role_grants                                              | 0                                      |
| Acl_roles                                                    | 0                                      |
| Acl_table_grants                                             | 0                                      |
| Acl_users                                                    | 6                                      |
| Aria_pagecache_blocks_not_flushed                            | 0                                      |
| Aria_pagecache_blocks_unused                                 | 15706                                  |
| Aria_pagecache_blocks_used                                   | 0                                      |
| Aria_pagecache_read_requests                                 | 0                                      |
| Aria_pagecache_reads                                         | 0                                      |
| Aria_pagecache_write_requests                                | 0                                      |
| Aria_pagecache_writes                                        | 0                                      |
| Aria_transaction_log_syncs                                   | 0                                      |
| Binlog_commits                                               | 0                                      |
| Binlog_group_commits                                         | 0                                      |
| Binlog_group_commit_trigger_count                            | 0                                      |
| Binlog_group_commit_trigger_lock_wait                        | 0                                      |
| Binlog_group_commit_trigger_timeout                          | 0                                      |
| Binlog_snapshot_file                                         |                                        |
| Binlog_snapshot_position                                     | 0                                      |
| Binlog_bytes_written                                         | 0                                      |
| Binlog_cache_disk_use                                        | 0                                      |
| Binlog_cache_use                                             | 0                                      |
| Binlog_stmt_cache_disk_use                                   | 0                                      |
| Binlog_stmt_cache_use                                        | 0                                      |
| Busy_time                                                    | 0.000000                               |
| Bytes_received                                               | 432                                    |
| Bytes_sent                                                   | 15183                                  |
| Com_admin_commands                                           | 1                                      |
| Com_alter_db                                                 | 0                                      |
| Com_alter_db_upgrade                                         | 0                                      |
| Com_alter_event                                              | 0                                      |
| Com_alter_function                                           | 0                                      |
| Com_alter_procedure                                          | 0                                      |
| Com_alter_server                                             | 0                                      |
| Com_alter_table                                              | 0                                      |
| Com_alter_tablespace                                         | 0                                      |
| Com_analyze                                                  | 0                                      |
| Com_assign_to_keycache                                       | 0                                      |
| Com_begin                                                    | 0                                      |
| Com_binlog                                                   | 0                                      |
| Com_call_procedure                                           | 0                                      |
| Com_change_db                                                | 0                                      |
| Com_change_master                                            | 0                                      |
| Com_check                                                    | 0                                      |
| Com_checksum                                                 | 0                                      |
| Com_commit                                                   | 0                                      |
| Com_compound_sql                                             | 0                                      |
| Com_create_db                                                | 0                                      |
| Com_create_event                                             | 0                                      |
| Com_create_function                                          | 0                                      |
| Com_create_index                                             | 0                                      |
| Com_create_procedure                                         | 0                                      |
| Com_create_role                                              | 0                                      |
| Com_create_server                                            | 0                                      |
| Com_create_table                                             | 0                                      |
| Com_create_temporary_table                                   | 0                                      |
| Com_create_trigger                                           | 0                                      |
| Com_create_udf                                               | 0                                      |
| Com_create_user                                              | 0                                      |
| Com_create_view                                              | 0                                      |
| Com_dealloc_sql                                              | 0                                      |
| Com_delete                                                   | 0                                      |
| Com_delete_multi                                             | 0                                      |
| Com_do                                                       | 0                                      |
| Com_drop_db                                                  | 0                                      |
| Com_drop_event                                               | 0                                      |
| Com_drop_function                                            | 0                                      |
| Com_drop_index                                               | 0                                      |
| Com_drop_procedure                                           | 0                                      |
| Com_drop_role                                                | 0                                      |
| Com_drop_server                                              | 0                                      |
| Com_drop_table                                               | 0                                      |
| Com_drop_temporary_table                                     | 0                                      |
| Com_drop_trigger                                             | 0                                      |
| Com_drop_user                                                | 0                                      |
| Com_drop_view                                                | 0                                      |
| Com_empty_query                                              | 0                                      |
| Com_execute_sql                                              | 0                                      |
| Com_flush                                                    | 0                                      |
| Com_get_diagnostics                                          | 0                                      |
| Com_grant                                                    | 0                                      |
| Com_grant_role                                               | 0                                      |
| Com_ha_close                                                 | 0                                      |
| Com_ha_open                                                  | 0                                      |
| Com_ha_read                                                  | 0                                      |
| Com_help                                                     | 0                                      |
| Com_insert                                                   | 0                                      |
| Com_insert_select                                            | 0                                      |
| Com_install_plugin                                           | 0                                      |
| Com_kill                                                     | 0                                      |
| Com_load                                                     | 0                                      |
| Com_lock_tables                                              | 0                                      |
| Com_optimize                                                 | 0                                      |
| Com_preload_keys                                             | 0                                      |
| Com_prepare_sql                                              | 0                                      |
| Com_purge                                                    | 0                                      |
| Com_purge_before_date                                        | 0                                      |
| Com_release_savepoint                                        | 0                                      |
| Com_rename_table                                             | 0                                      |
| Com_rename_user                                              | 0                                      |
| Com_repair                                                   | 0                                      |
| Com_replace                                                  | 0                                      |
| Com_replace_select                                           | 0                                      |
| Com_reset                                                    | 0                                      |
| Com_resignal                                                 | 0                                      |
| Com_revoke                                                   | 0                                      |
| Com_revoke_all                                               | 0                                      |
| Com_revoke_role                                              | 0                                      |
| Com_rollback                                                 | 0                                      |
| Com_rollback_to_savepoint                                    | 0                                      |
| Com_savepoint                                                | 0                                      |
| Com_select                                                   | 1                                      |
| Com_set_option                                               | 0                                      |
| Com_show_authors                                             | 0                                      |
| Com_show_binlog_events                                       | 0                                      |
| Com_show_binlogs                                             | 0                                      |
| Com_show_charsets                                            | 0                                      |
| Com_show_collations                                          | 0                                      |
| Com_show_contributors                                        | 0                                      |
| Com_show_create_db                                           | 0                                      |
| Com_show_create_event                                        | 0                                      |
| Com_show_create_func                                         | 0                                      |
| Com_show_create_proc                                         | 0                                      |
| Com_show_create_table                                        | 0                                      |
| Com_show_create_trigger                                      | 0                                      |
| Com_show_databases                                           | 0                                      |
| Com_show_engine_logs                                         | 0                                      |
| Com_show_engine_mutex                                        | 0                                      |
| Com_show_engine_status                                       | 0                                      |
| Com_show_errors                                              | 0                                      |
| Com_show_events                                              | 0                                      |
| Com_show_explain                                             | 0                                      |
| Com_show_fields                                              | 0                                      |
| Com_show_function_status                                     | 0                                      |
| Com_show_generic                                             | 0                                      |
| Com_show_grants                                              | 0                                      |
| Com_show_keys                                                | 0                                      |
| Com_show_master_status                                       | 0                                      |
| Com_show_open_tables                                         | 0                                      |
| Com_show_plugins                                             | 0                                      |
| Com_show_privileges                                          | 0                                      |
| Com_show_procedure_status                                    | 0                                      |
| Com_show_processlist                                         | 0                                      |
| Com_show_profile                                             | 0                                      |
| Com_show_profiles                                            | 0                                      |
| Com_show_relaylog_events                                     | 0                                      |
| Com_show_slave_hosts                                         | 0                                      |
| Com_show_slave_status                                        | 0                                      |
| Com_show_status                                              | 2                                      |
| Com_show_storage_engines                                     | 0                                      |
| Com_show_table_status                                        | 0                                      |
| Com_show_tables                                              | 0                                      |
| Com_show_triggers                                            | 0                                      |
| Com_show_variables                                           | 0                                      |
| Com_show_warnings                                            | 0                                      |
| Com_shutdown                                                 | 0                                      |
| Com_signal                                                   | 0                                      |
| Com_start_all_slaves                                         | 0                                      |
| Com_start_slave                                              | 0                                      |
| Com_stmt_close                                               | 0                                      |
| Com_stmt_execute                                             | 0                                      |
| Com_stmt_fetch                                               | 0                                      |
| Com_stmt_prepare                                             | 0                                      |
| Com_stmt_reprepare                                           | 0                                      |
| Com_stmt_reset                                               | 0                                      |
| Com_stmt_send_long_data                                      | 0                                      |
| Com_stop_all_slaves                                          | 0                                      |
| Com_stop_slave                                               | 0                                      |
| Com_truncate                                                 | 0                                      |
| Com_uninstall_plugin                                         | 0                                      |
| Com_unlock_tables                                            | 0                                      |
| Com_update                                                   | 0                                      |
| Com_update_multi                                             | 0                                      |
| Com_xa_commit                                                | 0                                      |
| Com_xa_end                                                   | 0                                      |
| Com_xa_prepare                                               | 0                                      |
| Com_xa_recover                                               | 0                                      |
| Com_xa_rollback                                              | 0                                      |
| Com_xa_start                                                 | 0                                      |
| Compression                                                  | OFF                                    |
| Connection_errors_accept                                     | 0                                      |
| Connection_errors_internal                                   | 0                                      |
| Connection_errors_max_connections                            | 0                                      |
| Connection_errors_peer_address                               | 0                                      |
| Connection_errors_select                                     | 0                                      |
| Connection_errors_tcpwrap                                    | 0                                      |
| Connections                                                  | 4                                      |
| Cpu_time                                                     | 0.000000                               |
| Created_tmp_disk_tables                                      | 0                                      |
| Created_tmp_files                                            | 6                                      |
| Created_tmp_tables                                           | 2                                      |
| Delayed_errors                                               | 0                                      |
| Delayed_insert_threads                                       | 0                                      |
| Delayed_writes                                               | 0                                      |
| Delete_scan                                                  | 0                                      |
| Empty_queries                                                | 0                                      |
| Executed_events                                              | 0                                      |
| Executed_triggers                                            | 0                                      |
| Feature_delay_key_write                                      | 0                                      |
| Feature_dynamic_columns                                      | 0                                      |
| Feature_fulltext                                             | 0                                      |
| Feature_gis                                                  | 0                                      |
| Feature_locale                                               | 0                                      |
| Feature_subquery                                             | 0                                      |
| Feature_timezone                                             | 0                                      |
| Feature_trigger                                              | 0                                      |
| Feature_xml                                                  | 0                                      |
| Flush_commands                                               | 1                                      |
| Handler_commit                                               | 1                                      |
| Handler_delete                                               | 0                                      |
| Handler_discover                                             | 0                                      |
| Handler_external_lock                                        | 0                                      |
| Handler_icp_attempts                                         | 0                                      |
| Handler_icp_match                                            | 0                                      |
| Handler_mrr_init                                             | 0                                      |
| Handler_mrr_key_refills                                      | 0                                      |
| Handler_mrr_rowid_refills                                    | 0                                      |
| Handler_prepare                                              | 0                                      |
| Handler_read_first                                           | 3                                      |
| Handler_read_key                                             | 0                                      |
| Handler_read_last                                            | 0                                      |
| Handler_read_next                                            | 0                                      |
| Handler_read_prev                                            | 0                                      |
| Handler_read_retry                                           | 0                                      |
| Handler_read_rnd                                             | 0                                      |
| Handler_read_rnd_deleted                                     | 0                                      |
| Handler_read_rnd_next                                        | 537                                    |
| Handler_rollback                                             | 0                                      |
| Handler_savepoint                                            | 0                                      |
| Handler_savepoint_rollback                                   | 0                                      |
| Handler_tmp_update                                           | 0                                      |
| Handler_tmp_write                                            | 516                                    |
| Handler_update                                               | 0                                      |
| Handler_write                                                | 0                                      |
| Innodb_available_undo_logs                                   | 128                                    |
| Innodb_background_log_sync                                   | 222                                    |
| Innodb_buffer_pool_bytes_data                                | 2523136                                |
| Innodb_buffer_pool_bytes_dirty                               | 0                                      |
| Innodb_buffer_pool_dump_status                               | Dumping buffer pool(s) not yet started |
| Innodb_buffer_pool_load_status                               | Loading buffer pool(s) not yet started |
| Innodb_buffer_pool_pages_data                                | 154                                    |
| Innodb_buffer_pool_pages_dirty                               | 0                                      |
| Innodb_buffer_pool_pages_flushed                             | 1                                      |
| Innodb_buffer_pool_pages_free                                | 8037                                   |
| Innodb_buffer_pool_pages_lru_flushed                         | 0                                      |
| Innodb_buffer_pool_pages_made_not_young                      | 0                                      |
| Innodb_buffer_pool_pages_made_young                          | 0                                      |
| Innodb_buffer_pool_pages_misc                                | 0                                      |
| Innodb_buffer_pool_pages_old                                 | 0                                      |
| Innodb_buffer_pool_pages_total                               | 8191                                   |
| Innodb_buffer_pool_read_ahead                                | 0                                      |
| Innodb_buffer_pool_read_ahead_evicted                        | 0                                      |
| Innodb_buffer_pool_read_ahead_rnd                            | 0                                      |
| Innodb_buffer_pool_read_requests                             | 558                                    |
| Innodb_buffer_pool_reads                                     | 155                                    |
| Innodb_buffer_pool_wait_free                                 | 0                                      |
| Innodb_buffer_pool_write_requests                            | 1                                      |
| Innodb_checkpoint_age                                        | 0                                      |
| Innodb_checkpoint_max_age                                    | 80826164                               |
| Innodb_data_fsyncs                                           | 5                                      |
| Innodb_data_pending_fsyncs                                   | 0                                      |
| Innodb_data_pending_reads                                    | 0                                      |
| Innodb_data_pending_writes                                   | 0                                      |
| Innodb_data_read                                             | 2609664                                |
| Innodb_data_reads                                            | 172                                    |
| Innodb_data_writes                                           | 5                                      |
| Innodb_data_written                                          | 34304                                  |
| Innodb_dblwr_pages_written                                   | 1                                      |
| Innodb_dblwr_writes                                          | 1                                      |
| Innodb_deadlocks                                             | 0                                      |
| Innodb_have_atomic_builtins                                  | ON                                     |
| Innodb_history_list_length                                   | 0                                      |
| Innodb_ibuf_discarded_delete_marks                           | 0                                      |
| Innodb_ibuf_discarded_deletes                                | 0                                      |
| Innodb_ibuf_discarded_inserts                                | 0                                      |
| Innodb_ibuf_free_list                                        | 0                                      |
| Innodb_ibuf_merged_delete_marks                              | 0                                      |
| Innodb_ibuf_merged_deletes                                   | 0                                      |
| Innodb_ibuf_merged_inserts                                   | 0                                      |
| Innodb_ibuf_merges                                           | 0                                      |
| Innodb_ibuf_segment_size                                     | 2                                      |
| Innodb_ibuf_size                                             | 1                                      |
| Innodb_log_waits                                             | 0                                      |
| Innodb_log_write_requests                                    | 0                                      |
| Innodb_log_writes                                            | 1                                      |
| Innodb_lsn_current                                           | 1616829                                |
| Innodb_lsn_flushed                                           | 1616829                                |
| Innodb_lsn_last_checkpoint                                   | 1616829                                |
| Innodb_master_thread_active_loops                            | 0                                      |
| Innodb_master_thread_idle_loops                              | 222                                    |
| Innodb_max_trx_id                                            | 2308                                   |
| Innodb_mem_adaptive_hash                                     | 2217568                                |
| Innodb_mem_dictionary                                        | 630703                                 |
| Innodb_mem_total                                             | 140771328                              |
| Innodb_mutex_os_waits                                        | 1                                      |
| Innodb_mutex_spin_rounds                                     | 30                                     |
| Innodb_mutex_spin_waits                                      | 1                                      |
| Innodb_oldest_view_low_limit_trx_id                          | 0                                      |
| Innodb_os_log_fsyncs                                         | 3                                      |
| Innodb_os_log_pending_fsyncs                                 | 0                                      |
| Innodb_os_log_pending_writes                                 | 0                                      |
| Innodb_os_log_written                                        | 512                                    |
| Innodb_page_size                                             | 16384                                  |
| Innodb_pages_created                                         | 0                                      |
| Innodb_pages_read                                            | 154                                    |
| Innodb_pages_written                                         | 1                                      |
| Innodb_purge_trx_id                                          | 0                                      |
| Innodb_purge_undo_no                                         | 0                                      |
| Innodb_read_views_memory                                     | 88                                     |
| Innodb_row_lock_current_waits                                | 0                                      |
| Innodb_row_lock_time                                         | 0                                      |
| Innodb_row_lock_time_avg                                     | 0                                      |
| Innodb_row_lock_time_max                                     | 0                                      |
| Innodb_row_lock_waits                                        | 0                                      |
| Innodb_rows_deleted                                          | 0                                      |
| Innodb_rows_inserted                                         | 0                                      |
| Innodb_rows_read                                             | 0                                      |
| Innodb_rows_updated                                          | 0                                      |
| Innodb_system_rows_deleted                                   | 0                                      |
| Innodb_system_rows_inserted                                  | 0                                      |
| Innodb_system_rows_read                                      | 0                                      |
| Innodb_system_rows_updated                                   | 0                                      |
| Innodb_s_lock_os_waits                                       | 2                                      |
| Innodb_s_lock_spin_rounds                                    | 60                                     |
| Innodb_s_lock_spin_waits                                     | 2                                      |
| Innodb_truncated_status_writes                               | 0                                      |
| Innodb_x_lock_os_waits                                       | 0                                      |
| Innodb_x_lock_spin_rounds                                    | 0                                      |
| Innodb_x_lock_spin_waits                                     | 0                                      |
| Innodb_page_compression_saved                                | 0                                      |
| Innodb_page_compression_trim_sect512                         | 0                                      |
| Innodb_page_compression_trim_sect1024                        | 0                                      |
| Innodb_page_compression_trim_sect2048                        | 0                                      |
| Innodb_page_compression_trim_sect4096                        | 0                                      |
| Innodb_page_compression_trim_sect8192                        | 0                                      |
| Innodb_page_compression_trim_sect16384                       | 0                                      |
| Innodb_page_compression_trim_sect32768                       | 0                                      |
| Innodb_num_index_pages_written                               | 0                                      |
| Innodb_num_non_index_pages_written                           | 5                                      |
| Innodb_num_pages_page_compressed                             | 0                                      |
| Innodb_num_page_compressed_trim_op                           | 0                                      |
| Innodb_num_page_compressed_trim_op_saved                     | 0                                      |
| Innodb_num_pages_page_decompressed                           | 0                                      |
| Innodb_num_pages_page_compression_error                      | 0                                      |
| Innodb_num_pages_encrypted                                   | 0                                      |
| Innodb_num_pages_decrypted                                   | 0                                      |
| Innodb_have_lz4                                              | OFF                                    |
| Innodb_have_lzo                                              | OFF                                    |
| Innodb_have_lzma                                             | OFF                                    |
| Innodb_have_bzip2                                            | OFF                                    |
| Innodb_have_snappy                                           | OFF                                    |
| Innodb_defragment_compression_failures                       | 0                                      |
| Innodb_defragment_failures                                   | 0                                      |
| Innodb_defragment_count                                      | 0                                      |
| Innodb_onlineddl_rowlog_rows                                 | 0                                      |
| Innodb_onlineddl_rowlog_pct_used                             | 0                                      |
| Innodb_onlineddl_pct_progress                                | 0                                      |
| Innodb_secondary_index_triggered_cluster_reads               | 0                                      |
| Innodb_secondary_index_triggered_cluster_reads_avoided       | 0                                      |
| Innodb_encryption_rotation_pages_read_from_cache             | 0                                      |
| Innodb_encryption_rotation_pages_read_from_disk              | 0                                      |
| Innodb_encryption_rotation_pages_modified                    | 0                                      |
| Innodb_encryption_rotation_pages_flushed                     | 0                                      |
| Innodb_encryption_rotation_estimated_iops                    | 0                                      |
| Innodb_scrub_background_page_reorganizations                 | 0                                      |
| Innodb_scrub_background_page_splits                          | 0                                      |
| Innodb_scrub_background_page_split_failures_underflow        | 0                                      |
| Innodb_scrub_background_page_split_failures_out_of_filespace | 0                                      |
| Innodb_scrub_background_page_split_failures_missing_index    | 0                                      |
| Innodb_scrub_background_page_split_failures_unknown          | 0                                      |
| Key_blocks_not_flushed                                       | 0                                      |
| Key_blocks_unused                                            | 107163                                 |
| Key_blocks_used                                              | 0                                      |
| Key_blocks_warm                                              | 0                                      |
| Key_read_requests                                            | 0                                      |
| Key_reads                                                    | 0                                      |
| Key_write_requests                                           | 0                                      |
| Key_writes                                                   | 0                                      |
| Last_query_cost                                              | 0.000000                               |
| Master_gtid_wait_count                                       | 0                                      |
| Master_gtid_wait_time                                        | 0                                      |
| Master_gtid_wait_timeouts                                    | 0                                      |
| Max_statement_time_exceeded                                  | 0                                      |
| Max_used_connections                                         | 1                                      |
| Memory_used                                                  | 273614696                              |
| Not_flushed_delayed_rows                                     | 0                                      |
| Open_files                                                   | 25                                     |
| Open_streams                                                 | 0                                      |
| Open_table_definitions                                       | 18                                     |
| Open_tables                                                  | 11                                     |
| Opened_files                                                 | 77                                     |
| Opened_plugin_libraries                                      | 0                                      |
| Opened_table_definitions                                     | 18                                     |
| Opened_tables                                                | 18                                     |
| Opened_views                                                 | 0                                      |
| Performance_schema_accounts_lost                             | 0                                      |
| Performance_schema_cond_classes_lost                         | 0                                      |
| Performance_schema_cond_instances_lost                       | 0                                      |
| Performance_schema_digest_lost                               | 0                                      |
| Performance_schema_file_classes_lost                         | 0                                      |
| Performance_schema_file_handles_lost                         | 0                                      |
| Performance_schema_file_instances_lost                       | 0                                      |
| Performance_schema_hosts_lost                                | 0                                      |
| Performance_schema_locker_lost                               | 0                                      |
| Performance_schema_mutex_classes_lost                        | 0                                      |
| Performance_schema_mutex_instances_lost                      | 0                                      |
| Performance_schema_rwlock_classes_lost                       | 0                                      |
| Performance_schema_rwlock_instances_lost                     | 0                                      |
| Performance_schema_session_connect_attrs_lost                | 0                                      |
| Performance_schema_socket_classes_lost                       | 0                                      |
| Performance_schema_socket_instances_lost                     | 0                                      |
| Performance_schema_stage_classes_lost                        | 0                                      |
| Performance_schema_statement_classes_lost                    | 0                                      |
| Performance_schema_table_handles_lost                        | 0                                      |
| Performance_schema_table_instances_lost                      | 0                                      |
| Performance_schema_thread_classes_lost                       | 0                                      |
| Performance_schema_thread_instances_lost                     | 0                                      |
| Performance_schema_users_lost                                | 0                                      |
| Prepared_stmt_count                                          | 0                                      |
| Qcache_free_blocks                                           | 1                                      |
| Qcache_free_memory                                           | 1031336                                |
| Qcache_hits                                                  | 0                                      |
| Qcache_inserts                                               | 0                                      |
| Qcache_lowmem_prunes                                         | 0                                      |
| Qcache_not_cached                                            | 0                                      |
| Qcache_queries_in_cache                                      | 0                                      |
| Qcache_total_blocks                                          | 1                                      |
| Queries                                                      | 4                                      |
| Questions                                                    | 4                                      |
| Rows_read                                                    | 10                                     |
| Rows_sent                                                    | 517                                    |
| Rows_tmp_read                                                | 516                                    |
| Rpl_status                                                   | AUTH_MASTER                            |
| Select_full_join                                             | 0                                      |
| Select_full_range_join                                       | 0                                      |
| Select_range                                                 | 0                                      |
| Select_range_check                                           | 0                                      |
| Select_scan                                                  | 2                                      |
| Slave_connections                                            | 0                                      |
| Slave_heartbeat_period                                       | 0.000                                  |
| Slave_open_temp_tables                                       | 0                                      |
| Slave_received_heartbeats                                    | 0                                      |
| Slave_retried_transactions                                   | 0                                      |
| Slave_running                                                | OFF                                    |
| Slave_skipped_errors                                         | 0                                      |
| Slaves_connected                                             | 0                                      |
| Slaves_running                                               | 0                                      |
| Slow_launch_threads                                          | 0                                      |
| Slow_queries                                                 | 0                                      |
| Sort_merge_passes                                            | 0                                      |
| Sort_priority_queue_sorts                                    | 0                                      |
| Sort_range                                                   | 0                                      |
| Sort_rows                                                    | 0                                      |
| Sort_scan                                                    | 0                                      |
| Ssl_accept_renegotiates                                      | 0                                      |
| Ssl_accepts                                                  | 0                                      |
| Ssl_callback_cache_hits                                      | 0                                      |
| Ssl_cipher                                                   |                                        |
| Ssl_cipher_list                                              |                                        |
| Ssl_client_connects                                          | 0                                      |
| Ssl_connect_renegotiates                                     | 0                                      |
| Ssl_ctx_verify_depth                                         | 0                                      |
| Ssl_ctx_verify_mode                                          | 0                                      |
| Ssl_default_timeout                                          | 0                                      |
| Ssl_finished_accepts                                         | 0                                      |
| Ssl_finished_connects                                        | 0                                      |
| Ssl_server_not_after                                         |                                        |
| Ssl_server_not_before                                        |                                        |
| Ssl_session_cache_hits                                       | 0                                      |
| Ssl_session_cache_misses                                     | 0                                      |
| Ssl_session_cache_mode                                       | NONE                                   |
| Ssl_session_cache_overflows                                  | 0                                      |
| Ssl_session_cache_size                                       | 0                                      |
| Ssl_session_cache_timeouts                                   | 0                                      |
| Ssl_sessions_reused                                          | 0                                      |
| Ssl_used_session_cache_entries                               | 0                                      |
| Ssl_verify_depth                                             | 0                                      |
| Ssl_verify_mode                                              | 0                                      |
| Ssl_version                                                  |                                        |
| Subquery_cache_hit                                           | 0                                      |
| Subquery_cache_miss                                          | 0                                      |
| Syncs                                                        | 2                                      |
| Table_locks_immediate                                        | 21                                     |
| Table_locks_waited                                           | 0                                      |
| Tc_log_max_pages_used                                        | 0                                      |
| Tc_log_page_size                                             | 4096                                   |
| Tc_log_page_waits                                            | 0                                      |
| Threadpool_idle_threads                                      | 0                                      |
| Threadpool_threads                                           | 0                                      |
| Threads_cached                                               | 0                                      |
| Threads_connected                                            | 1                                      |
| Threads_created                                              | 2                                      |
| Threads_running                                              | 1                                      |
| Update_scan                                                  | 0                                      |
| Uptime                                                       | 223                                    |
| Uptime_since_flush_status                                    | 223                                    |
| wsrep_cluster_conf_id                                        | 18446744073709551615                   |
| wsrep_cluster_size                                           | 0                                      |
| wsrep_cluster_state_uuid                                     |                                        |
| wsrep_cluster_status                                         | Disconnected                           |
| wsrep_connected                                              | OFF                                    |
| wsrep_local_bf_aborts                                        | 0                                      |
| wsrep_local_index                                            | 18446744073709551615                   |
| wsrep_provider_name                                          |                                        |
| wsrep_provider_vendor                                        |                                        |
| wsrep_provider_version                                       |                                        |
| wsrep_ready                                                  | OFF                                    |
| wsrep_thread_count                                           | 0                                      |
+--------------------------------------------------------------+----------------------------------------+
516 rows in set (0.00 sec)

Example of filtered output:

SHOW STATUS LIKE 'Key%';
+------------------------+--------+
| Variable_name          | Value  |
+------------------------+--------+
| Key_blocks_not_flushed | 0      |
| Key_blocks_unused      | 107163 |
| Key_blocks_used        | 0      |
| Key_blocks_warm        | 0      |
| Key_read_requests      | 0      |
| Key_reads              | 0      |
| Key_write_requests     | 0      |
| Key_writes             | 0      |
+------------------------+--------+
8 rows in set (0.00 sec)

1.1.2.8.49 SHOW TABLE STATUS

Syntax

SHOW TABLE STATUS [{FROM | IN} db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW TABLE STATUS works like SHOW TABLES, but provides more extensive information about each non-TEMPORARY table.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The following information is returned:

ColumnDescription
NameTable name.
EngineTable storage engine.
VersionVersion number from the table's .frm file.
Row_formatRow format (see InnoDB, Aria and MyISAM row formats).
RowsNumber of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate.
Avg_row_lengthAverage row length in the table.
Data_lengthFor InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory.
Max_data_lengthMaximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB.
Index_lengthLength of the index file.
Data_freeBytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table.
Auto_incrementNext AUTO_INCREMENT value.
Create_timeTime the table was created.
Update_timeTime the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE.
Check_timeTime the table was last checked. Not kept by all storage engines, in which case will be NULL.
CollationCharacter set and collation.
ChecksumLive checksum value, if any.
Create_optionsExtra CREATE TABLE options.
CommentTable comment provided when MariaDB created the table.
Max_index_lengthMaximum index length (supported by MyISAM and Aria tables). Added in MariaDB 10.3.5.
TemporaryPlaceholder to signal that a table is a temporary table. Currently always "N", except "Y" for generated information_schema tables and NULL for views. Added in MariaDB 10.3.5.

Similar information can be found in the information_schema.TABLES table as well as by using mysqlshow:

mysqlshow --status db_name

Example

show table status\G
*************************** 1. row ***************************
           Name: bus_routes
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 5
 Avg_row_length: 3276
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2017-05-24 11:17:46
    Update_time: NULL
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options: 
        Comment:

1.1.2.8.50 SHOW TABLES

Syntax

SHOW [FULL] TABLES [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW TABLES lists the non-TEMPORARY tables, sequences and views in a given database.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. For example, when searching for tables in the test database, the column name for use in the WHERE and LIKE clauses will be Tables_in_test

The FULL modifier is supported such that SHOW FULL TABLES displays a second output column. Values for the second column. Table_type, are BASE TABLE for a table, VIEW for a view and SEQUENCE for a sequence.

You can also get this information using:

mysqlshow db_name

See mysqlshow for more details.

If you have no privileges for a base table or view, it does not show up in the output from SHOW TABLES or mysqlshow db_name.

The information_schema.TABLES table, as well as the SHOW TABLE STATUS statement, provide extended information about tables.

Examples

SHOW TABLES;
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
| t1                   |
| view1                |
+----------------------+

Showing the tables beginning with a only.

SHOW TABLES WHERE Tables_in_test LIKE 'a%';
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
+----------------------+

Showing tables and table types:

SHOW FULL TABLES;
+----------------+------------+
| Tables_in_test | Table_type |
+----------------+------------+
| s1             | SEQUENCE   |
| student        | BASE TABLE |
| v1             | VIEW       |
+----------------+------------+

See Also

1.1.2.8.51 SHOW TABLE_STATISTICS

Syntax

SHOW TABLE_STATISTICS

Description

The SHOW TABLE_STATISTICS statementis part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.TABLE_STATISTICS table shows statistics on table usage

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.TABLE_STATISTICS articles for more information.

Example

SHOW TABLE_STATISTICS\G
*************************** 1. row ***************************
           Table_schema: mysql
             Table_name: proxies_priv
              Rows_read: 2
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 2. row ***************************
           Table_schema: test
             Table_name: employees_example
              Rows_read: 7
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 3. row ***************************
           Table_schema: mysql
             Table_name: user
              Rows_read: 16
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 4. row ***************************
           Table_schema: mysql
             Table_name: db
              Rows_read: 2
           Rows_changed: 0
Rows_changed_x_#indexes: 0

1.1.2.8.52 SHOW TRIGGERS

Syntax

SHOW TRIGGERS [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW TRIGGERS lists the triggers currently defined for tables in a database (the default database unless a FROM clause is given). This statement requires the TRIGGER privilege (prior to MySQL 5.1.22, it required the SUPER privilege).

The LIKE clause, if present on its own, indicates which table names to match and causes the statement to display triggers for those tables. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Similar information is stored in the information_schema.TRIGGERS table.

MariaDB starting with 10.2.3

If there are multiple triggers for the same action, then the triggers are shown in action order.

Examples

For the trigger defined at Trigger Overview:

SHOW triggers Like 'animals' \G
*************************** 1. row ***************************
             Trigger: the_mooses_are_loose
               Event: INSERT
               Table: animals
           Statement: BEGIN
 IF NEW.name = 'Moose' THEN
  UPDATE animal_count SET animal_count.animals = animal_count.animals+100;
 ELSE 
  UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
 END IF;
END
              Timing: AFTER
             Created: 2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Listing all triggers associated with a certain table:

SHOW TRIGGERS FROM test WHERE `Table` = 'user' \G
*************************** 1. row ***************************
             Trigger: user_ai
               Event: INSERT
               Table: user
           Statement: BEGIN END
              Timing: AFTER
             Created:  2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@%
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci
SHOW triggers WHERE Event Like 'Insert' \G
*************************** 1. row ***************************
             Trigger: the_mooses_are_loose
               Event: INSERT
               Table: animals
           Statement: BEGIN
 IF NEW.name = 'Moose' THEN
  UPDATE animal_count SET animal_count.animals = animal_count.animals+100;
 ELSE 
  UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
 END IF;
END
              Timing: AFTER
             Created: 2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci
  • character_set_client is the session value of the character_set_client system variable when the trigger was created.
  • collation_connection is the session value of the collation_connection system variable when the trigger was created.
  • Database Collation is the collation of the database with which the trigger is associated.

These columns were added in MariaDB/MySQL 5.1.21.

Old triggers created before MySQL 5.7 and MariaDB 10.2.3 has NULL in the Created column.

See also

1.1.2.8.53 SHOW USER_STATISTICS

Syntax

SHOW USER_STATISTICS

Description

The SHOW USER_STATISTICS statement is part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.USER_STATISTICS table holds statistics about user activity. You can use this table to find out such things as which user is causing the most load and which users are being abusive. You can also use this table to measure how close to capacity the server may be.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.USER_STATISTICS table for more information.

Example

SHOW USER_STATISTICS\G
*************************** 1. row ***************************
                  User: root
     Total_connections: 1
Concurrent_connections: 0
        Connected_time: 3297
             Busy_time: 0.14113400000000006
              Cpu_time: 0.017637000000000003
        Bytes_received: 969
            Bytes_sent: 22355
  Binlog_bytes_written: 0
             Rows_read: 10
             Rows_sent: 67
          Rows_deleted: 0
         Rows_inserted: 0
          Rows_updated: 0
       Select_commands: 7
       Update_commands: 0
        Other_commands: 0
   Commit_transactions: 1
 Rollback_transactions: 0
    Denied_connections: 0
      Lost_connections: 0
         Access_denied: 0
         Empty_queries: 7

1.1.2.8.54 SHOW VARIABLES

Syntax

SHOW [GLOBAL | SESSION] VARIABLES
    [LIKE 'pattern' | WHERE expr]

Description

SHOW VARIABLES shows the values of MariaDB system variables. This information also can be obtained using the mysqladmin variables command. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions.

With the GLOBAL modifier, SHOW VARIABLES displays the values that are used for new connections to MariaDB. With SESSION, it displays the values that are in effect for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. With a LIKE clause, the statement displays only rows for those variables with names that match the pattern. To obtain the row for a specific variable, use a LIKE clause as shown:

SHOW VARIABLES LIKE 'maria_group_commit';
SHOW SESSION VARIABLES LIKE 'maria_group_commit';

To get a list of variables whose name match a pattern, use the "%" wildcard character in a LIKE clause:

SHOW VARIABLES LIKE '%maria%';
SHOW GLOBAL VARIABLES LIKE '%maria%';

Wildcard characters can be used in any position within the pattern to be matched. Strictly speaking, because "_" is a wildcard that matches any single character, you should escape it as "\_" to match it literally. In practice, this is rarely necessary.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

See SET for information on setting server system variables.

See Server System Variables for a list of all the variables that can be set.

You can also see the server variables by querying the Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES tables.

Examples

SHOW VARIABLES LIKE 'aria%';
+------------------------------------------+---------------------+
| Variable_name                            | Value               |
+------------------------------------------+---------------------+
| aria_block_size                          | 8192                |
| aria_checkpoint_interval                 | 30                  |
| aria_checkpoint_log_activity             | 1048576             |
| aria_force_start_after_recovery_failures | 0                   |
| aria_group_commit                        | none                |
| aria_group_commit_interval               | 0                   |
| aria_log_file_size                       | 1073741824          |
| aria_log_purge_type                      | immediate           |
| aria_max_sort_file_size                  | 9223372036853727232 |
| aria_page_checksum                       | ON                  |
| aria_pagecache_age_threshold             | 300                 |
| aria_pagecache_buffer_size               | 134217728           |
| aria_pagecache_division_limit            | 100                 |
| aria_recover                             | NORMAL              |
| aria_repair_threads                      | 1                   |
| aria_sort_buffer_size                    | 134217728           |
| aria_stats_method                        | nulls_unequal       |
| aria_sync_log_dir                        | NEWFILE             |
| aria_used_for_temp_tables                | ON                  |
+------------------------------------------+---------------------+
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
  INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
  VARIABLE_NAME LIKE 'max_error_count' OR
  VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 64           |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

SET GLOBAL max_error_count=128;

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
  INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
  VARIABLE_NAME LIKE 'max_error_count' OR
  VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 128          |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

SET GLOBAL max_error_count=128;

SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 64    |
+-----------------+-------+

SHOW GLOBAL VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 128   |
+-----------------+-------+

Because the following variable only has a global scope, the global value is returned even when specifying SESSION (in this case by default):

SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 30    |
+------------------------+-------+

1.1.2.8.55 SHOW WARNINGS

Syntax

SHOW WARNINGS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) WARNINGS

Description

SHOW WARNINGS shows the error, warning, and note messages that resulted from the last statement that generated messages in the current session. It shows nothing if the last statement used a table and generated no messages. (That is, a statement that uses a table but generates no messages clears the message list.) Statements that do not use tables and do not generate messages have no effect on the message list.

A note is different to a warning in that it only appears if the sql_notes variable is set to 1 (the default), and is not converted to an error if strict mode is enabled.

A related statement, SHOW ERRORS, shows only the errors.

The SHOW COUNT(*) WARNINGS statement displays the total number of errors, warnings, and notes. You can also retrieve this number from the warning_count variable:

SHOW COUNT(*) WARNINGS;
SELECT @@warning_count;

The value of warning_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored.

The LIMIT clause has the same syntax as for the SELECT statement.

SHOW WARNINGS can be used after EXPLAIN EXTENDED to see how a query is internally rewritten by MariaDB.

If the sql_notes server variable is set to 1, Notes are included in the output of SHOW WARNINGS; if it is set to 0, this statement will not show (or count) Notes.

The results of SHOW WARNINGS and SHOW COUNT(*) WARNINGS are directly sent to the client. If you need to access those information in a stored program, you can use the GET DIAGNOSTICS statement instead.

For a list of MariaDB error codes, see MariaDB Error Codes.

The mysql client also has a number of options related to warnings. The \W command will show warnings after every statement, while \w will disable this. Starting the client with the --show-warnings option will show warnings after every statement.

MariaDB 10.3.1 implements a stored routine error stack trace. SHOW WARNINGS can also be used to show more information. See the example below.

Examples

SELECT 1/0;
+------+
| 1/0  |
+------+
| NULL |
+------+

SHOW COUNT(*) WARNINGS;
+-------------------------+
| @@session.warning_count |
+-------------------------+
|                       1 |
+-------------------------+

SHOW WARNINGS;
+---------+------+---------------+
| Level   | Code | Message       |
+---------+------+---------------+
| Warning | 1365 | Division by 0 |
+---------+------+---------------+

Stack Trace

From MariaDB 10.3.1, displaying a stack trace:

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
  BEGIN
    DECLARE c CURSOR FOR SELECT * FROM not_existing;
    OPEN c;
    CLOSE c;
  END;
$$
CREATE OR REPLACE PROCEDURE p2()
  BEGIN
    CALL p1;
  END;
$$
DELIMITER ;
CALL p2;
ERROR 1146 (42S02): Table 'test.not_existing' doesn't exist

SHOW WARNINGS;
+-------+------+-----------------------------------------+
| Level | Code | Message                                 |
+-------+------+-----------------------------------------+
| Error | 1146 | Table 'test.not_existing' doesn't exist |
| Note  | 4091 | At line 6 in test.p1                    |
| Note  | 4091 | At line 4 in test.p2                    |
+-------+------+-----------------------------------------+

SHOW WARNINGS displays a stack trace, showing where the error actually happened:

  • Line 4 in test.p1 is the OPEN command which actually raised the error
  • Line 3 in test.p2 is the CALL statement, calling p1 from p2.

See Also

1.1.2.8.56 SHOW WSREP_MEMBERSHIP

SHOW WSREP_MEMBERSHIP is part of the WSREP_INFO plugin.

Syntax

SHOW WSREP_MEMBERSHIP

Description

The SHOW WSREP_MEMBERSHIP statement returns Galera node cluster membership information. It returns the same information as found in the information_schema.WSREP_MEMBERSHIP table. Only users with the SUPER privilege can access this information.

Examples

SHOW WSREP_MEMBERSHIP;
+-------+--------------------------------------+----------+-----------------+
| Index | Uuid                                 | Name     | Address         |
+-------+--------------------------------------+----------+-----------------+
|     0 | 19058073-8940-11e4-8570-16af7bf8fced | my_node1 | 10.0.2.15:16001 |
|     1 | 19f2b0e0-8942-11e4-9cb8-b39e8ee0b5dd | my_node3 | 10.0.2.15:16003 |
|     2 | d85e62db-8941-11e4-b1ef-4bc9980e476d | my_node2 | 10.0.2.15:16002 |
+-------+--------------------------------------+----------+-----------------+

1.1.2.8.57 SHOW WSREP_STATUS

SHOW WSREP_STATUS is part of the WSREP_INFO plugin.

Syntax

SHOW WSREP_STATUS

Description

The SHOW WSREP_STATUS statement returns Galera node and cluster status information. It returns the same information as found in the information_schema.WSREP_STATUS table. Only users with the SUPER privilege can access this information.

Examples

SHOW WSREP_STATUS;
+------------+-------------+----------------+--------------+
| Node_Index | Node_Status | Cluster_Status | Cluster_Size |
+------------+-------------+----------------+--------------+
|          0 | Synced      | Primary        |            3 |
+------------+-------------+----------------+--------------+

1.1.2.9 System Tables

1.1.2.9.1 Information Schema

1.1.2.9.1.1 Information Schema Tables

1.1.2.9.1.1.1 Information Schema InnoDB Tables

1.1.2.9.1.1.1.1 Information Schema INNODB_BUFFER_PAGE Table

The Information Schema INNODB_BUFFER_PAGE table contains information about pages in the buffer pool.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
BLOCK_IDBuffer Pool Block identifier.
SPACETablespace identifier. Matches the SPACE value in the INNODB_SYS_TABLES table.
PAGE_NUMBERBuffer pool page number.
PAGE_TYPEPage type; one of allocated (newly-allocated page), index (B-tree node), undo_log (undo log page), inode (index node), ibuf_free_list (insert buffer free list), ibuf_bitmap (insert buffer bitmap), system (system page), trx_system (transaction system data), file_space_header (file space header), extent_descriptor (extent descriptor page), blob (uncompressed blob page), compressed_blob (first compressed blob page), compressed_blob2 (subsequent compressed blob page) or unknown.
FLUSH_TYPEFlush type.
FIX_COUNTCount of the threads using this block in the buffer pool. When it is zero, the block can be evicted from the buffer pool.
IS_HASHEDWhether or not a hash index has been built on this page.
NEWEST_MODIFICATIONMost recent modification's Log Sequence Number.
OLDEST_MODIFICATIONOldest modification's Log Sequence Number.
ACCESS_TIMEAbstract number representing the time the page was first accessed.
TABLE_NAMETable that the page belongs to.
INDEX_NAMEIndex that the page belongs to, either a clustered index or a secondary index.
NUMBER_RECORDSNumber of records the page contains.
DATA_SIZESize in bytes of all the records contained in the page.
COMPRESSED_SIZECompressed size in bytes of the page, or NULL for pages that aren't compressed.
PAGE_STATEPage state; one of FILE_PAGE (page from a file) or MEMORY (page from an in-memory object) for valid data, or one of NULL, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXWhether there is I/O pending for the page; one of IO_NONE (no pending I/O), IO_READ (read pending), IO_WRITE (write pending).
IS_OLDWhether the page is old or not.
FREE_PAGE_CLOCKFreed_page_clock counter, which tracks the number of blocks removed from the end of the least recently used (LRU) list, at the time the block was last placed at the head of the list.

The related INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU table contains the same information, but with an LRU (least recently used) position rather than block id.

Examples

DESC information_schema.innodb_buffer_page;
+---------------------+---------------------+------+-----+---------+-------+
| Field               | Type                | Null | Key | Default | Extra |
+---------------------+---------------------+------+-----+---------+-------+
| POOL_ID             | bigint(21) unsigned | NO   |     | 0       |       |
| BLOCK_ID            | bigint(21) unsigned | NO   |     | 0       |       |
| SPACE               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_NUMBER         | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_TYPE           | varchar(64)         | YES  |     | NULL    |       |
| FLUSH_TYPE          | bigint(21) unsigned | NO   |     | 0       |       |
| FIX_COUNT           | bigint(21) unsigned | NO   |     | 0       |       |
| IS_HASHED           | varchar(3)          | YES  |     | NULL    |       |
| NEWEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| OLDEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| ACCESS_TIME         | bigint(21) unsigned | NO   |     | 0       |       |
| TABLE_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| INDEX_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| NUMBER_RECORDS      | bigint(21) unsigned | NO   |     | 0       |       |
| DATA_SIZE           | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED_SIZE     | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_STATE          | varchar(64)         | YES  |     | NULL    |       |
| IO_FIX              | varchar(64)         | YES  |     | NULL    |       |
| IS_OLD              | varchar(3)          | YES  |     | NULL    |       |
| FREE_PAGE_CLOCK     | bigint(21) unsigned | NO   |     | 0       |       |
+---------------------+---------------------+------+-----+---------+-------+
SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE\G
...
*************************** 6. row ***************************
            POOL_ID: 0
           BLOCK_ID: 5
              SPACE: 0
        PAGE_NUMBER: 11
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: NO
NEWEST_MODIFICATION: 2046835
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 2585566280
         TABLE_NAME: `SYS_INDEXES`
         INDEX_NAME: CLUST_IND
     NUMBER_RECORDS: 57
          DATA_SIZE: 4016
    COMPRESSED_SIZE: 0
         PAGE_STATE: FILE_PAGE
             IO_FIX: IO_NONE
             IS_OLD: NO
    FREE_PAGE_CLOCK: 0
...

1.1.2.9.1.1.1.2 Information Schema INNODB_BUFFER_PAGE_LRU Table

The Information Schema INNODB_BUFFER_PAGE_LRU table contains information about pages in the buffer pool and how they are ordered for eviction purposes.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
LRU_POSITIONLRU (Least recently-used), for determining eviction order from the buffer pool.
SPACETablespace identifier. Matches the SPACE value on the INNODB_SYS_TABLES table.
PAGE_NUMBERBuffer pool page number.
PAGE_TYPEPage type; one of allocated (newly-allocated page), index (B-tree node), undo_log (undo log page), inode (index node), ibuf_free_list (insert buffer free list), ibuf_bitmap (insert buffer bitmap), system (system page), trx_system (transaction system data), file_space_header (file space header), extent_descriptor (extent descriptor page), blob (uncompressed blob page), compressed_blob (first compressed blob page), compressed_blob2 (subsequent compressed blob page) or unknown.
FLUSH_TYPEFlush type.
FIX_COUNTCount of the threads using this block in the buffer pool. When it is zero, the block can be evicted from the buffer pool.
IS_HASHEDWhether or not a hash index has been built on this page.
NEWEST_MODIFICATIONMost recent modification's Log Sequence Number.
OLDEST_MODIFICATIONOldest modification's Log Sequence Number.
ACCESS_TIMEAbstract number representing the time the page was first accessed.
TABLE_NAMETable that the page belongs to.
INDEX_NAMEIndex that the page belongs to, either a clustered index or a secondary index.
NUMBER_RECORDSNumber of records the page contains.
DATA_SIZESize in bytes of all the records contained in the page.
COMPRESSED_SIZECompressed size in bytes of the page, or NULL for pages that aren't compressed.
PAGE_STATEPage state; one of FILE_PAGE (page from a file) or MEMORY (page from an in-memory object) for valid data, or one of NULL, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXWhether there is I/O pending for the page; one of IO_NONE (no pending I/O), IO_READ (read pending), IO_WRITE (write pending).
IS_OLDWhether the page is old or not.
FREE_PAGE_CLOCKFreed_page_clock counter, which tracks the number of blocks removed from the end of the LRU list, at the time the block was last placed at the head of the list.

The related INFORMATION_SCHEMA.INNODB_BUFFER_PAGE table contains the same information, but with a block id rather than LRU position.

Example

DESC information_schema.innodb_buffer_page_lru;
+---------------------+---------------------+------+-----+---------+-------+
| Field               | Type                | Null | Key | Default | Extra |
+---------------------+---------------------+------+-----+---------+-------+
| POOL_ID             | bigint(21) unsigned | NO   |     | 0       |       |
| LRU_POSITION        | bigint(21) unsigned | NO   |     | 0       |       |
| SPACE               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_NUMBER         | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_TYPE           | varchar(64)         | YES  |     | NULL    |       |
| FLUSH_TYPE          | bigint(21) unsigned | NO   |     | 0       |       |
| FIX_COUNT           | bigint(21) unsigned | NO   |     | 0       |       |
| IS_HASHED           | varchar(3)          | YES  |     | NULL    |       |
| NEWEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| OLDEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| ACCESS_TIME         | bigint(21) unsigned | NO   |     | 0       |       |
| TABLE_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| INDEX_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| NUMBER_RECORDS      | bigint(21) unsigned | NO   |     | 0       |       |
| DATA_SIZE           | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED_SIZE     | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED          | varchar(3)          | YES  |     | NULL    |       |
| IO_FIX              | varchar(64)         | YES  |     | NULL    |       |
| IS_OLD              | varchar(3)          | YES  |     | NULL    |       |
| FREE_PAGE_CLOCK     | bigint(21) unsigned | NO   |     | 0       |       |
+---------------------+---------------------+------+-----+---------+-------+
SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU\G
...
*************************** 6. row ***************************
            POOL_ID: 0
       LRU_POSITION: 5
              SPACE: 0
        PAGE_NUMBER: 11
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: NO
NEWEST_MODIFICATION: 2046835
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 2585566280
         TABLE_NAME: `SYS_INDEXES`
         INDEX_NAME: CLUST_IND
     NUMBER_RECORDS: 57
          DATA_SIZE: 4016
    COMPRESSED_SIZE: 0
         COMPRESSED: NO
             IO_FIX: IO_NONE
             IS_OLD: NO
    FREE_PAGE_CLOCK: 0
...

1.1.2.9.1.1.1.3 Information Schema INNODB_BUFFER_POOL_PAGES Table

The Information Schema INNODB_BUFFER_POOL_PAGES table is a Percona enhancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains a record for each page in the buffer pool.

It has the following columns:

ColumnDescription
PAGE_TYPEType of page; one of index, undo_log, inode, ibuf_free_list, allocated, bitmap, sys, trx_sys, fsp_hdr, xdes, blob, zblob, zblob2 and unknown.
SPACE_IDTablespace ID.
PAGE_NOPage offset within tablespace.
LRU_POSITIONPage position in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.2.9.1.1.1.4 Information Schema INNODB_BUFFER_POOL_PAGES_BLOB Table

The Information Schema INNODB_BUFFER_POOL_PAGES_BLOB table is a Percona enchancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains information about buffer pool blob pages.

It has the following columns:

ColumnDescription
SPACE_IDTablespace ID.
PAGE_NOPage offset within tablespace.
COMPRESSED1 if the blob contains compressed data, 0 if not.
PART_LENPage data length.
NEXT_PAGE_NONext page number.
LRU_POSITIONPage position in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.2.9.1.1.1.5 Information Schema INNODB_BUFFER_POOL_PAGES_INDEX Table

The Information Schema INNODB_BUFFER_POOL_PAGES table is a Percona enhancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains information about buffer pool index pages.

It has the following columns:

ColumnDescription
INDEX_IDIndex name
SPACE_IDTablespace ID
PAGE_NOPage offset within tablespace.
N_RECSNumber of user records on the page.
DATA_SIZETotal data size in bytes of records in the page.
HASHED1 if the block is in the adaptive hash index, 0 if not.
ACCESS_TIMEPage's last access time.
MODIFIED1 if the page has been modified since being loaded, 0 if not.
DIRTY1 if the page has been modified since it was last flushed, 0 if not
OLD1 if the page in the in the old blocks of the LRU (least-recently-used) list, 0 if not.
LRU_POSITIONPosition in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.2.9.1.1.1.6 Information Schema INNODB_BUFFER_POOL_STATS Table

The Information Schema INNODB_BUFFER_POOL_STATS table contains information about pages in the buffer pool, similar to what is returned with the SHOW ENGINE INNODB STATUS statement.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
POOL_SIZESize in pages of the buffer pool.
FREE_BUFFERSNumber of free pages in the buffer pool.
DATABASE_PAGESTotal number of pages in the buffer pool.
OLD_DATABASE_PAGESNumber of pages in the old sublist.
MODIFIED_DATABASE_PAGESNumber of dirty pages.
PENDING_DECOMPRESSNumber of pages pending decompression.
PENDING_READSPending buffer pool level reads.
PENDING_FLUSH_LRUNumber of pages in the LRU pending flush.
PENDING_FLUSH_LISTNumber of pages in the flush list pending flush.
PAGES_MADE_YOUNGPages moved from the old sublist to the new sublist.
PAGES_NOT_MADE_YOUNGPages that have remained in the old sublist without moving to the new sublist.
PAGES_MADE_YOUNG_RATEHits that cause blocks to move to the top of the new sublist.
PAGES_MADE_NOT_YOUNG_RATEHits that do not cause blocks to move to the top of the new sublist due to the innodb_old_blocks delay not being met.
NUMBER_PAGES_READNumber of pages read.
NUMBER_PAGES_CREATEDNumber of pages created.
NUMBER_PAGES_WRITTENNumber of pages written.
PAGES_READ_RATENumber of pages read since the last printout divided by the time elapsed, giving pages read per second.
PAGES_CREATE_RATENumber of pages created since the last printout divided by the time elapsed, giving pages created per second.
PAGES_WRITTEN_RATENumber of pages written since the last printout divided by the time elapsed, giving pages written per second.
NUMBER_PAGES_GETNumber of logical read requests.
HIT_RATEBuffer pool hit rate.
YOUNG_MAKE_PER_THOUSAND_GETSFor every 1000 gets, the number of pages made young.
NOT_YOUNG_MAKE_PER_THOUSAND_GETSFor every 1000 gets, the number of pages not made young.
NUMBER_PAGES_READ_AHEADNumber of pages read ahead.
NUMBER_READ_AHEAD_EVICTEDNumber of pages read ahead by the read-ahead thread that were later evicted without being accessed by any queries.
READ_AHEAD_RATEPages read ahead since the last printout divided by the time elapsed, giving read-ahead rate per second.
READ_AHEAD_EVICTED_RATERead-ahead pages not accessed since the last printout divided by time elapsed, giving the number of read-ahead pages evicted without access per second.
LRU_IO_TOTALTotal least-recently used I/O.
LRU_IO_CURRENTLeast-recently used I/O for the current interval.
UNCOMPRESS_TOTALTotal number of pages decompressed.
UNCOMPRESS_CURRENTNumber of pages decompressed in the current interval

Examples

DESC information_schema.innodb_buffer_pool_stats;
+----------------------------------+---------------------+------+-----+---------+-------+
| Field                            | Type                | Null | Key | Default | Extra |
+----------------------------------+---------------------+------+-----+---------+-------+
| POOL_ID                          | bigint(21) unsigned | NO   |     | 0       |       |
| POOL_SIZE                        | bigint(21) unsigned | NO   |     | 0       |       |
| FREE_BUFFERS                     | bigint(21) unsigned | NO   |     | 0       |       |
| DATABASE_PAGES                   | bigint(21) unsigned | NO   |     | 0       |       |
| OLD_DATABASE_PAGES               | bigint(21) unsigned | NO   |     | 0       |       |
| MODIFIED_DATABASE_PAGES          | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_DECOMPRESS               | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_READS                    | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_FLUSH_LRU                | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_FLUSH_LIST               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_MADE_YOUNG                 | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_NOT_MADE_YOUNG             | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_MADE_YOUNG_RATE            | double              | NO   |     | 0       |       |
| PAGES_MADE_NOT_YOUNG_RATE        | double              | NO   |     | 0       |       |
| NUMBER_PAGES_READ                | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_CREATED             | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_WRITTEN             | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_READ_RATE                  | double              | NO   |     | 0       |       |
| PAGES_CREATE_RATE                | double              | NO   |     | 0       |       |
| PAGES_WRITTEN_RATE               | double              | NO   |     | 0       |       |
| NUMBER_PAGES_GET                 | bigint(21) unsigned | NO   |     | 0       |       |
| HIT_RATE                         | bigint(21) unsigned | NO   |     | 0       |       |
| YOUNG_MAKE_PER_THOUSAND_GETS     | bigint(21) unsigned | NO   |     | 0       |       |
| NOT_YOUNG_MAKE_PER_THOUSAND_GETS | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_READ_AHEAD          | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_READ_AHEAD_EVICTED        | bigint(21) unsigned | NO   |     | 0       |       |
| READ_AHEAD_RATE                  | double              | NO   |     | 0       |       |
| READ_AHEAD_EVICTED_RATE          | double              | NO   |     | 0       |       |
| LRU_IO_TOTAL                     | bigint(21) unsigned | NO   |     | 0       |       |
| LRU_IO_CURRENT                   | bigint(21) unsigned | NO   |     | 0       |       |
| UNCOMPRESS_TOTAL                 | bigint(21) unsigned | NO   |     | 0       |       |
| UNCOMPRESS_CURRENT               | bigint(21) unsigned | NO   |     | 0       |       |
+----------------------------------+---------------------+------+-----+---------+-------+

1.1.2.9.1.1.1.7 Information Schema INNODB_CHANGED_PAGES Table

The Information Schema INNODB_CHANGED_PAGES Table contains data about modified pages from the bitmap file. It is updated at checkpoints by the log tracking thread parsing the log, so does not contain real-time data.

The number of records is limited by the value of the innodb_max_changed_pages system variable.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACE_IDModified page space id
PAGE_IDModified page id
START_LSNInterval start after which page was changed (equal to checkpoint LSN)
END_LSNInterval end before which page was changed (equal to checkpoint LSN)

1.1.2.9.1.1.1.8 Information Schema INNODB_CMP and INNODB_CMP_RESET Tables

The INNODB_CMP and INNODB_CMP_RESET tables contain status information on compression operations related to compressed XtraDB/InnoDB tables.

The PROCESS privilege is required to query this table.

These tables contain the following columns:

Column NameDescription
PAGE_SIZECompressed page size, in bytes. This value is unique in the table; other values are totals which refer to pages of this size.
COMPRESS_OPSHow many times a page of the size PAGE_SIZE has been compressed. This happens when a new page is created because the compression log runs out of space. This value includes both successful operations and compression failures.
COMPRESS_OPS_OKHow many times a page of the size PAGE_SIZE has been successfully compressed. This value should be as close as possible to COMPRESS_OPS. If it is notably lower, either avoid compressing some tables, or increase the KEY_BLOCK_SIZE for some compressed tables.
COMPRESS_TIMETime (in seconds) spent to compress pages of the size PAGE_SIZE. This value includes time spent in compression failures.
UNCOMPRESS_OPSHow many times a page of the size PAGE_SIZE has been uncompressed. This happens when an uncompressed version of a page is created in the buffer pool, or when a compression failure occurs.
UNCOMPRESS_TIMETime (in seconds) spent to uncompress pages of the size PAGE_SIZE.

These tables can be used to measure the effectiveness of XtraDB/InnoDB table compression. When you have to decide a value for KEY_BLOCK_SIZE, you can create more than one version of the table (one for each candidate value) and run a realistic workload on them. Then, these tables can be used to see how the operations performed with different page sizes.

INNODB_CMP and INNODB_CMP_RESET have the same columns and always contain the same values, but when INNODB_CMP_RESET is queried, both the tables are cleared. INNODB_CMP_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMP can be used to see the cumulated statistics.

Examples

SELECT * FROM information_schema.INNODB_CMP\G
**************************** 1. row *****************************
      page_size: 1024
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
...

See Also

Other tables that can be used to monitor XtraDB/InnoDB compressed tables:

1.1.2.9.1.1.1.9 Information Schema INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables contain status information on compressed pages in the buffer pool (see InnoDB COMPRESSED format).

The PROCESS privilege is required to query this table.

These tables contain the following columns:

Column NameDescription
PAGE_SIZECompressed page size, in bytes. This value is unique in the table; other values are totals which refer to pages of this size.
BUFFER_POOL_INSTANCEBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
PAGES_USEDNumber of pages of the size PAGE_SIZE which are currently in the buffer pool.
PAGES_FREENumber of pages of the size PAGE_SIZE which are currently free, and thus are available for allocation. This value represents the buffer pool's fragmentation. A totally unfragmented buffer pool has at most 1 free page.
RELOCATION_OPSHow many times a page of the size PAGE_SIZE has been relocated. This happens when data exceeds a page (because a row must be copied into a new page) and when two pages are merged (because their data shrunk and can now be contained in one page).
RELOCATION_TIMETime (in seconds) spent in relocation operations for pages of the size PAGE_SIZE. This column is reset when the INNODB_CMPMEM_RESET table is queried.

These tables can be used to measure the effectiveness of InnoDB table compression. When you have to decide a value for KEY_BLOCK_SIZE, you can create more than one version of the table (one for each candidate value) and run a realistic workload on them. Then, these tables can be used to see how the operations performed with different page sizes.

INNODB_CMPMEM and INNODB_CMPMEM_RESET have the same columns and always contain the same values, but when INNODB_CMPMEM_RESET is queried, the RELOCATION_TIME column from both the tables are cleared. INNODB_CMPMEM_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMPMEM can be used to see the cumulated statistics.

Example

SELECT * FROM information_schema.INNODB_CMPMEM\G
********************** 1. row **********************
            page_size: 1024
 buffer_pool_instance: 0
           pages_used: 0
           pages_free: 0
      reloacation_ops: 0
      relocation_time: 0

See Also

Other tables that can be used to monitor InnoDB compressed tables:

1.1.2.9.1.1.1.10 Information Schema INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables

The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables contain status information on compression operations related to compressed XtraDB/InnoDB tables, grouped by individual indexes. These tables are only populated if the innodb_cmp_per_index_enabled system variable is set to ON.

The PROCESS privilege is required to query this table.

These tables contains the following columns:

Column NameDescription
DATABASE_NAMEDatabase containing the index.
TABLE_NAMETable containing the index.
INDEX_NAMEOther values are totals which refer to this index's compression.
COMPRESS_OPSHow many times a page of INDEX_NAME has been compressed. This happens when a new page is created because the compression log runs out of space. This value includes both successful operations and compression failures.
COMPRESS_OPS_OKHow many times a page of INDEX_NAME has been successfully compressed. This value should be as close as possible to COMPRESS_OPS. If it is notably lower, either avoid compressing some tables, or increase the KEY_BLOCK_SIZE for some compressed tables.
COMPRESS_TIMETime (in seconds) spent to compress pages of the size PAGE_SIZE. This value includes time spent in compression failures.
UNCOMPRESS_OPSHow many times a page of INDEX_NAME has been uncompressed. This happens when an uncompressed version of a page is created in the buffer pool, or when a compression failure occurs.
UNCOMPRESS_TIMETime (in seconds) spent to uncompress pages of INDEX_NAME.

These tables can be used to measure the effectiveness of XtraDB/InnoDB compression, per table or per index. The values in these tables show which tables perform better with index compression, and which tables cause too many compression failures or perform too many compression/uncompression operations. When compression performs badly for a table, this might mean that you should change its KEY_BLOCK_SIZE, or that the table should not be compressed.

INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET have the same columns and always contain the same values, but when INNODB_CMP_PER_INDEX_RESET is queried, both the tables are cleared. INNODB_CMP_PER_INDEX_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMP_PER_INDEX can be used to see the cumulated statistics.

See Also

Other tables that can be used to monitor XtraDB/InnoDB compressed tables:

1.1.2.9.1.1.1.11 Information Schema INNODB_FT_BEING_DELETED Table

The Information Schema INNODB_FT_BEING_DELETED table is only used while document ID's in the related INNODB_FT_DELETED are being removed from an InnoDB fulltext index while an OPTIMIZE TABLE is underway. At all other times the table will be empty.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following column:

ColumnDescription
DOC_IDDocument ID of the row being deleted. Either an underlying ID value, or a sequence value generated by InnoDB if no usable option exists.

1.1.2.9.1.1.1.12 Information Schema INNODB_FT_CONFIG Table

The Information Schema INNODB_FT_CONFIG table contains InnoDB fulltext index metadata.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
KEYMetadata item name.
VALUEAssociated value.

Example

SELECT * FROM INNODB_FT_CONFIG;
+---------------------------+-------+
| KEY                       | VALUE |
+---------------------------+-------+
| optimize_checkpoint_limit | 180   |
| synced_doc_id             | 6     |
| last_optimized_word       |       |
| deleted_doc_count         | 0     |
| total_word_count          |       |
| optimize_start_time       |       |
| optimize_end_time         |       |
| stopword_table_name       |       |
| use_stopword              | 1     |
| table_state               | 0     |
+---------------------------+-------+

1.1.2.9.1.1.1.13 Information Schema INNODB_FT_DEFAULT_STOPWORD Table

The Information Schema INNODB_FT_DEFAULT_STOPWORD table contains a list of default stopwords used when creating an InnoDB fulltext index.

The PROCESS privilege is required to view the table.

It has the following column:

ColumnDescription
VALUEDefault stopword for an InnoDB fulltext index. Setting either the innodb_ft_server_stopword_table or the innodb_ft_user_stopword_table system variable will override this.

Example

SELECT * FROM information_schema.INNODB_FT_DEFAULT_STOPWORD\G
*************************** 1. row ***************************
value: a
*************************** 2. row ***************************
value: about
*************************** 3. row ***************************
value: an
*************************** 4. row ***************************
value: are
...
*************************** 36. row ***************************
value: www

1.1.2.9.1.1.1.14 Information Schema INNODB_FT_DELETED Table

The Information Schema INNODB_FT_DELETED table contains rows that have been deleted from an InnoDB fulltext index. This information is then used to filter results on subsequent searches, removing the need to expensively reorganise the index each time a row is deleted.

The fulltext index is then only reorganized when an OPTIMIZE TABLE statement is underway. The related INNODB_FT_BEING_DELETED table contains rows being deleted while an OPTIMIZE TABLE is in the process of running.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following column:

ColumnDescription
DOC_IDDocument ID of the deleted row deleted. Either an underlying ID value, or a sequence value generated by InnoDB if no usable option exists.

Example

SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      2 |
+--------+

DELETE FROM test.ft_innodb LIMIT 1;

SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      2 |
|      3 |
+--------+

1.1.2.9.1.1.1.15 Information Schema INNODB_FT_INDEX_CACHE Table

The Information Schema INNODB_FT_INDEX_CACHE table contains information about rows that have recently been inserted into an InnoDB fulltext index. To avoid re-organizing the fulltext index each time a change is made, which would be very expensive, new changes are stored separately and only integrated when an OPTIMIZE TABLE is run.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
WORDWord from the text of a newly added row. Words can appear multiple times in the table, once per DOC_ID and POSITION combination.
FIRST_DOC_IDFirst document ID where this word appears in the index.
LAST_DOC_IDLast document ID where this word appears in the index.
DOC_COUNTNumber of rows containing this word in the index.
DOC_IDDocument ID of the newly added row, either an appropriate ID column or an internal InnoDB value.
POSITIONPosition of this word instance within the DOC_ID, as an offset added to the previous POSITION instance.

Note that for OPTIMIZE TABLE to process InnoDB fulltext index data, the innodb_optimize_fulltext_only system variable needs to be set to 1. When this is done, and an OPTIMIZE TABLE statement run, the INNODB_FT_INDEX_CACHE table will be emptied, and the INNODB_FT_INDEX_TABLE table will be updated.

Examples

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           4 |         1 |      4 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           1 |         1 |      1 |        4 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+
9 rows in set (0.00 sec)

INSERT INTO test.ft_innodb VALUES(3,'And she ate a pear');

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+
OPTIMIZE TABLE test.ft_innodb\G
*************************** 1. row ***************************
   Table: test.ft_innodb
      Op: optimize
Msg_type: note
Msg_text: Table does not support optimize, doing recreate + analyze instead
*************************** 2. row ***************************
   Table: test.ft_innodb
      Op: optimize
Msg_type: status
Msg_text: OK
2 rows in set (2.24 sec)

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+
13 rows in set (0.00 sec)

The OPTIMIZE TABLE statement has no effect, because the innodb_optimize_fulltext_only variable wasn't set:

SHOW VARIABLES LIKE 'innodb_optimize_fulltext_only';
+-------------------------------+-------+
| Variable_name                 | Value |
+-------------------------------+-------+
| innodb_optimize_fulltext_only | OFF   |
+-------------------------------+-------+

SET GLOBAL innodb_optimize_fulltext_only =1;

OPTIMIZE TABLE test.ft_innodb;
+----------------+----------+----------+----------+
| Table          | Op       | Msg_type | Msg_text |
+----------------+----------+----------+----------+
| test.ft_innodb | optimize | status   | OK       |
+----------------+----------+----------+----------+

SELECT * FROM INNODB_FT_INDEX_CACHE;
Empty set (0.00 sec)

1.1.2.9.1.1.1.16 Information Schema INNODB_FT_INDEX_TABLE Table

The Information Schema INNODB_FT_INDEX_TABLE table contains information about InnoDB fulltext indexes. To avoid re-organizing the fulltext index each time a change is made, which would be very expensive, new changes are stored separately and only integrated when an OPTIMIZE TABLE is run. See the INNODB_FT_INDEX_CACHE table.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
WORDWord from the text of a column with a fulltext index. Words can appear multiple times in the table, once per DOC_ID and POSITION combination.
FIRST_DOC_IDFirst document ID where this word appears in the index.
LAST_DOC_IDLast document ID where this word appears in the index.
DOC_COUNTNumber of rows containing this word in the index.
DOC_IDDocument ID of the newly added row, either an appropriate ID column or an internal InnoDB value.
POSITIONPosition of this word instance within the DOC_ID, as an offset added to the previous POSITION instance.

Note that for OPTIMIZE TABLE to process InnoDB fulltext index data, the innodb_optimize_fulltext_only system variable needs to be set to 1. When this is done, and an OPTIMIZE TABLE statement run, the INNODB_FT_INDEX_CACHE table will be emptied, and the INNODB_FT_INDEX_TABLE table will be updated.

Examples

SELECT * FROM INNODB_FT_INDEX_TABLE;
Empty set (0.00 sec)

SET GLOBAL innodb_optimize_fulltext_only =1;

OPTIMIZE TABLE test.ft_innodb;
+----------------+----------+----------+----------+
| Table          | Op       | Msg_type | Msg_text |
+----------------+----------+----------+----------+
| test.ft_innodb | optimize | status   | OK       |
+----------------+----------+----------+----------+

SELECT * FROM INNODB_FT_INDEX_TABLE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+

1.1.2.9.1.1.1.17 Information Schema INNODB_LOCK_WAITS Table

The Information Schema INNODB_LOCK_WAITS table contains information about blocked InnoDB transactions. The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
REQUESTING_TRX_IDRequesting transaction ID from the INNODB_TRX table.
REQUESTED_LOCK_IDLock ID from the INNODB.LOCKS table for the waiting transaction.
BLOCKING_TRX_IDBlocking transaction ID from the INNODB_TRX table.
BLOCKING_LOCK_IDLock ID from the INNODB.LOCKS table of a lock held by a transaction that is blocking another transaction.

The table is often used in conjunction with the INNODB_LOCKS and INNODB_TRX tables to diagnose problematic locks and transactions.

1.1.2.9.1.1.1.18 Information Schema INNODB_LOCKS Table

The Information Schema INNODB_LOCKS table stores information about locks that InnoDB transactions have requested but not yet acquired, or that are blocking another transaction.

It has the following columns:

ColumnDescription
LOCK_IDLock ID number - the format is not fixed, so do not rely upon the number for information.
LOCK_TRX_IDLock's transaction ID. Matches the INNODB_TRX.TRX_ID column.
LOCK_MODELock mode. One of S (shared), X (exclusive), IS (intention shared), IX (intention exclusive row lock), S_GAP (shared gap lock), X_GAP (exclusive gap lock), IS_GAP (intention shared gap lock), IX_GAP (intention exclusive gap lock) or AUTO_INC (auto-increment table level lock).
LOCK_TYPEWhether the lock is RECORD (row level) or TABLE level.
LOCK_TABLEName of the locked table,or table containing locked rows.
LOCK_INDEXIndex name if a RECORD LOCK_TYPE, or NULL if not.
LOCK_SPACETablespace ID if a RECORD LOCK_TYPE, or NULL if not.
LOCK_PAGELocked record page number if a RECORD LOCK_TYPE, or NULL if not.
LOCK_RECLocked record heap number if a RECORD LOCK_TYPE, or NULL if not.
LOCK_DATALocked record primary key as an SQL string if a RECORD LOCK_TYPE, or NULL if not. If no primary key exists, the internal InnoDB row_id number is instead used. To avoid unnecessary IO, also NULL if the locked record page is not in the buffer pool

The table is often used in conjunction with the INNODB_LOCK_WAITS and INNODB_TRX tables to diagnose problematic locks and transactions

Example

-- session 1
START TRANSACTION;
UPDATE t SET id = 15 WHERE id = 10;

-- session 2
DELETE FROM t WHERE id = 10;

-- session 1
USE information_schema;
SELECT l.*, t.*
    FROM information_schema.INNODB_LOCKS l
    JOIN information_schema.INNODB_TRX t
        ON l.lock_trx_id = t.trx_id
    WHERE trx_state = 'LOCK WAIT' \G
*************************** 1. row ***************************
                   lock_id: 840:40:3:2
               lock_trx_id: 840
                 lock_mode: X
                 lock_type: RECORD
                lock_table: `test`.`t`
                lock_index: PRIMARY
                lock_space: 40
                 lock_page: 3
                  lock_rec: 2
                 lock_data: 10
                    trx_id: 840
                 trx_state: LOCK WAIT
               trx_started: 2019-12-23 18:43:46
     trx_requested_lock_id: 840:40:3:2
          trx_wait_started: 2019-12-23 18:43:46
                trx_weight: 2
       trx_mysql_thread_id: 46
                 trx_query: DELETE FROM t WHERE id = 10
       trx_operation_state: starting index read
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 2
     trx_lock_memory_bytes: 1136
           trx_rows_locked: 1
         trx_rows_modified: 0
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
          trx_is_read_only: 0
trx_autocommit_non_locking: 0

.

1.1.2.9.1.1.1.19 Information Schema INNODB_METRICS Table

The Information Schema INNODB_METRICS table contains a list of useful InnoDB performance metrics. Each row in the table represents an instrumented counter that can be stopped, started and reset, and which can be grouped together by module.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
NAMEUnique counter name.
SUBSYSTEMInnoDB subsystem. See below for the matching module to use to enable/disable monitoring this subsytem with the innodb_monitor_enable and innodb_monitor_disable system variables.
COUNTCount since being enabled.
MAX_COUNTMaximum value since being enabled.
MIN_COUNTMinimum value since being enabled.
AVG_COUNTAverage value since being enabled.
COUNT_RESETCount since last being reset.
MAX_COUNT_RESETMaximum value since last being reset.
MIN_COUNT_RESETMinimum value since last being reset.
AVG_COUNT_RESETAverage value since last being reset.
TIME_ENABLEDTime last enabled.
TIME_DISABLEDTime last disabled
TIME_ELAPSEDTime since enabled
TIME_RESETTime last reset.
STATUSWhether the counter is currently enabled to disabled.
TYPEItem type; one of counter, value, status_counter, set_owner, set_member.
COMMENTCounter description.

Enabling and Disabling Counters

Most of the counters are disabled by default. To enable them, use the innodb_monitor_enable system variable. You can either enable a variable by its name, for example:

SET GLOBAL innodb_monitor_enable = icp_match;

or enable a number of counters grouped by module. The SUBSYSTEM field indicates which counters are grouped together, but the following module names need to be used:

Module NameSubsytem Field
module_metadatametadata
module_locklock
module_bufferbuffer
module_buf_pagebuffer_page_io
module_osos
module_trxtransaction
module_purgepurge
module_compresscompression
module_filefile_system
module_indexindex
module_adaptive_hashadaptive_hash_index From MariaDB 10.6.2, if innodb_adaptive_hash_index is disabled (the default), adaptive_hash_index will not be updated.
module_ibuf_systemchange_buffer
module_srvserver
module_ddlddl
module_dmldml
module_logrecovery
module_icpicp

There are four counters in the icp subsystem:

SELECT NAME, SUBSYSTEM FROM INNODB_METRICS WHERE SUBSYSTEM='icp';
+------------------+-----------+
| NAME             | SUBSYSTEM |
+------------------+-----------+
| icp_attempts     | icp       |
| icp_no_match     | icp       |
| icp_out_of_range | icp       |
| icp_match        | icp       |
+------------------+-----------+

To enable them all, use the associated module name from the table above, module_icp.

SET GLOBAL innodb_monitor_enable = module_icp;

The % wildcard, used to represent any number of characters, can also be used when naming counters, for example:

SET GLOBAL innodb_monitor_enable = 'buffer%'

To disable counters, use the innodb_monitor_disable system variable, using the same naming rules as described above for enabling.

Counter status is not persistent, and will be reset when the server restarts. It is possible to use the options on the command line, or the innodb_monitor_enable option only in a configuration file.

Resetting Counters

Counters can also be reset. Resetting sets all the *_COUNT_RESET values to zero, while leaving the *_COUNT values, which perform counts since the counter was enabled, untouched. Resetting is performed with the innodb_monitor_reset (for individual counters) and innodb_monitor_reset_all (for all counters) system variables.

Simplifying from MariaDB 10.6

MariaDB starting with 10.6

From MariaDB 10.6, the interface was simplified by removing the following:

  • buffer_LRU_batches_flush
  • buffer_LRU_batch_flush_pages
  • buffer_LRU_batches_evict
  • buffer_LRU_batch_evict_pages

and by making the following reflect the status variables:

The intention is to eventually remove the interface entirely (see MDEV-15706).

Examples

Until MariaDB 10.5:

SELECT name,subsystem,type,comment FROM INFORMATION_SCHEMA.INNODB_METRICS;
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| name                                       | subsystem           | type           | comment                                                                                                          |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| metadata_table_handles_opened              | metadata            | counter        | Number of table handles opened                                                                                   |
| metadata_table_handles_closed              | metadata            | counter        | Number of table handles closed                                                                                   |
| metadata_table_reference_count             | metadata            | counter        | Table reference counter                                                                                          |
| lock_deadlocks                             | lock                | counter        | Number of deadlocks                                                                                              |
| lock_timeouts                              | lock                | counter        | Number of lock timeouts                                                                                          |
| lock_rec_lock_waits                        | lock                | counter        | Number of times enqueued into record lock wait queue                                                             |
| lock_table_lock_waits                      | lock                | counter        | Number of times enqueued into table lock wait queue                                                              |
| lock_rec_lock_requests                     | lock                | counter        | Number of record locks requested                                                                                 |
| lock_rec_lock_created                      | lock                | counter        | Number of record locks created                                                                                   |
| lock_rec_lock_removed                      | lock                | counter        | Number of record locks removed from the lock queue                                                               |
| lock_rec_locks                             | lock                | counter        | Current number of record locks on tables                                                                         |
| lock_table_lock_created                    | lock                | counter        | Number of table locks created                                                                                    |
| lock_table_lock_removed                    | lock                | counter        | Number of table locks removed from the lock queue                                                                |
| lock_table_locks                           | lock                | counter        | Current number of table locks on tables                                                                          |
| lock_row_lock_current_waits                | lock                | status_counter | Number of row locks currently being waited for (innodb_row_lock_current_waits)                                   |
| lock_row_lock_time                         | lock                | status_counter | Time spent in acquiring row locks, in milliseconds (innodb_row_lock_time)                                        |
| lock_row_lock_time_max                     | lock                | value          | The maximum time to acquire a row lock, in milliseconds (innodb_row_lock_time_max)                               |
| lock_row_lock_waits                        | lock                | status_counter | Number of times a row lock had to be waited for (innodb_row_lock_waits)                                          |
| lock_row_lock_time_avg                     | lock                | value          | The average time to acquire a row lock, in milliseconds (innodb_row_lock_time_avg)                               |
| buffer_pool_size                           | server              | value          | Server buffer pool size (all buffer pools) in bytes                                                              |
| buffer_pool_reads                          | buffer              | status_counter | Number of reads directly from disk (innodb_buffer_pool_reads)                                                    |
| buffer_pool_read_requests                  | buffer              | status_counter | Number of logical read requests (innodb_buffer_pool_read_requests)                                               |
| buffer_pool_write_requests                 | buffer              | status_counter | Number of write requests (innodb_buffer_pool_write_requests)                                                     |
| buffer_pool_wait_free                      | buffer              | status_counter | Number of times waited for free buffer (innodb_buffer_pool_wait_free)                                            |
| buffer_pool_read_ahead                     | buffer              | status_counter | Number of pages read as read ahead (innodb_buffer_pool_read_ahead)                                               |
| buffer_pool_read_ahead_evicted             | buffer              | status_counter | Read-ahead pages evicted without being accessed (innodb_buffer_pool_read_ahead_evicted)                          |
| buffer_pool_pages_total                    | buffer              | value          | Total buffer pool size in pages (innodb_buffer_pool_pages_total)                                                 |
| buffer_pool_pages_misc                     | buffer              | value          | Buffer pages for misc use such as row locks or the adaptive hash index (innodb_buffer_pool_pages_misc)           |
| buffer_pool_pages_data                     | buffer              | value          | Buffer pages containing data (innodb_buffer_pool_pages_data)                                                     |
| buffer_pool_bytes_data                     | buffer              | value          | Buffer bytes containing data (innodb_buffer_pool_bytes_data)                                                     |
| buffer_pool_pages_dirty                    | buffer              | value          | Buffer pages currently dirty (innodb_buffer_pool_pages_dirty)                                                    |
| buffer_pool_bytes_dirty                    | buffer              | value          | Buffer bytes currently dirty (innodb_buffer_pool_bytes_dirty)                                                    |
| buffer_pool_pages_free                     | buffer              | value          | Buffer pages currently free (innodb_buffer_pool_pages_free)                                                      |
| buffer_pages_created                       | buffer              | status_counter | Number of pages created (innodb_pages_created)                                                                   |
| buffer_pages_written                       | buffer              | status_counter | Number of pages written (innodb_pages_written)                                                                   |
| buffer_index_pages_written                 | buffer              | status_counter | Number of index pages written (innodb_index_pages_written)                                                       |
| buffer_non_index_pages_written             | buffer              | status_counter | Number of non index pages written (innodb_non_index_pages_written)                                               |
| buffer_pages_read                          | buffer              | status_counter | Number of pages read (innodb_pages_read)                                                                         |
| buffer_index_sec_rec_cluster_reads         | buffer              | status_counter | Number of secondary record reads triggered cluster read                                                          |
| buffer_index_sec_rec_cluster_reads_avoided | buffer              | status_counter | Number of secondary record reads avoided triggering cluster read                                                 |
| buffer_data_reads                          | buffer              | status_counter | Amount of data read in bytes (innodb_data_reads)                                                                 |
| buffer_data_written                        | buffer              | status_counter | Amount of data written in bytes (innodb_data_written)                                                            |
| buffer_flush_batch_scanned                 | buffer              | set_owner      | Total pages scanned as part of flush batch                                                                       |
| buffer_flush_batch_num_scan                | buffer              | set_member     | Number of times buffer flush list flush is called                                                                |
| buffer_flush_batch_scanned_per_call        | buffer              | set_member     | Pages scanned per flush batch scan                                                                               |
| buffer_flush_batch_total_pages             | buffer              | set_owner      | Total pages flushed as part of flush batch                                                                       |
| buffer_flush_batches                       | buffer              | set_member     | Number of flush batches                                                                                          |
| buffer_flush_batch_pages                   | buffer              | set_member     | Pages queued as a flush batch                                                                                    |
| buffer_flush_neighbor_total_pages          | buffer              | set_owner      | Total neighbors flushed as part of neighbor flush                                                                |
| buffer_flush_neighbor                      | buffer              | set_member     | Number of times neighbors flushing is invoked                                                                    |
| buffer_flush_neighbor_pages                | buffer              | set_member     | Pages queued as a neighbor batch                                                                                 |
| buffer_flush_n_to_flush_requested          | buffer              | counter        | Number of pages requested for flushing.                                                                          |
| buffer_flush_n_to_flush_by_age             | buffer              | counter        | Number of pages target by LSN Age for flushing.                                                                  |
| buffer_flush_adaptive_avg_time             | buffer              | counter        | Avg time (ms) spent for adaptive flushing recently.                                                              |
| buffer_flush_adaptive_avg_pass             | buffer              | counter        | Number of adaptive flushes passed during the recent Avg period.                                                  |
| buffer_LRU_get_free_loops                  | buffer              | counter        | Total loops in LRU get free.                                                                                     |
| buffer_LRU_get_free_waits                  | buffer              | counter        | Total sleep waits in LRU get free.                                                                               |
| buffer_flush_avg_page_rate                 | buffer              | counter        | Average number of pages at which flushing is happening                                                           |
| buffer_flush_lsn_avg_rate                  | buffer              | counter        | Average redo generation rate                                                                                     |
| buffer_flush_pct_for_dirty                 | buffer              | counter        | Percent of IO capacity used to avoid max dirty page limit                                                        |
| buffer_flush_pct_for_lsn                   | buffer              | counter        | Percent of IO capacity used to avoid reusable redo space limit                                                   |
| buffer_flush_sync_waits                    | buffer              | counter        | Number of times a wait happens due to sync flushing                                                              |
| buffer_flush_adaptive_total_pages          | buffer              | set_owner      | Total pages flushed as part of adaptive flushing                                                                 |
| buffer_flush_adaptive                      | buffer              | set_member     | Number of adaptive batches                                                                                       |
| buffer_flush_adaptive_pages                | buffer              | set_member     | Pages queued as an adaptive batch                                                                                |
| buffer_flush_sync_total_pages              | buffer              | set_owner      | Total pages flushed as part of sync batches                                                                      |
| buffer_flush_sync                          | buffer              | set_member     | Number of sync batches                                                                                           |
| buffer_flush_sync_pages                    | buffer              | set_member     | Pages queued as a sync batch                                                                                     |
| buffer_flush_background_total_pages        | buffer              | set_owner      | Total pages flushed as part of background batches                                                                |
| buffer_flush_background                    | buffer              | set_member     | Number of background batches                                                                                     |
| buffer_flush_background_pages              | buffer              | set_member     | Pages queued as a background batch                                                                               |
| buffer_LRU_batch_scanned                   | buffer              | set_owner      | Total pages scanned as part of LRU batch                                                                         |
| buffer_LRU_batch_num_scan                  | buffer              | set_member     | Number of times LRU batch is called                                                                              |
| buffer_LRU_batch_scanned_per_call          | buffer              | set_member     | Pages scanned per LRU batch call                                                                                 |
| buffer_LRU_batch_flush_total_pages         | buffer              | set_owner      | Total pages flushed as part of LRU batches                                                                       |
| buffer_LRU_batches_flush                   | buffer              | set_member     | Number of LRU batches                                                                                            |
| buffer_LRU_batch_flush_pages               | buffer              | set_member     | Pages queued as an LRU batch                                                                                     |
| buffer_LRU_batch_evict_total_pages         | buffer              | set_owner      | Total pages evicted as part of LRU batches                                                                       |
| buffer_LRU_batches_evict                   | buffer              | set_member     | Number of LRU batches                                                                                            |
| buffer_LRU_batch_evict_pages               | buffer              | set_member     | Pages queued as an LRU batch                                                                                     |
| buffer_LRU_single_flush_failure_count      | Buffer              | counter        | Number of times attempt to flush a single page from LRU failed                                                   |
| buffer_LRU_get_free_search                 | Buffer              | counter        | Number of searches performed for a clean page                                                                    |
| buffer_LRU_search_scanned                  | buffer              | set_owner      | Total pages scanned as part of LRU search                                                                        |
| buffer_LRU_search_num_scan                 | buffer              | set_member     | Number of times LRU search is performed                                                                          |
| buffer_LRU_search_scanned_per_call         | buffer              | set_member     | Page scanned per single LRU search                                                                               |
| buffer_LRU_unzip_search_scanned            | buffer              | set_owner      | Total pages scanned as part of LRU unzip search                                                                  |
| buffer_LRU_unzip_search_num_scan           | buffer              | set_member     | Number of times LRU unzip search is performed                                                                    |
| buffer_LRU_unzip_search_scanned_per_call   | buffer              | set_member     | Page scanned per single LRU unzip search                                                                         |
| buffer_page_read_index_leaf                | buffer_page_io      | counter        | Number of Index Leaf Pages read                                                                                  |
| buffer_page_read_index_non_leaf            | buffer_page_io      | counter        | Number of Index Non-leaf Pages read                                                                              |
| buffer_page_read_index_ibuf_leaf           | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages read                                                                    |
| buffer_page_read_index_ibuf_non_leaf       | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages read                                                                |
| buffer_page_read_undo_log                  | buffer_page_io      | counter        | Number of Undo Log Pages read                                                                                    |
| buffer_page_read_index_inode               | buffer_page_io      | counter        | Number of Index Inode Pages read                                                                                 |
| buffer_page_read_ibuf_free_list            | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages read                                                                     |
| buffer_page_read_ibuf_bitmap               | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages read                                                                        |
| buffer_page_read_system_page               | buffer_page_io      | counter        | Number of System Pages read                                                                                      |
| buffer_page_read_trx_system                | buffer_page_io      | counter        | Number of Transaction System Pages read                                                                          |
| buffer_page_read_fsp_hdr                   | buffer_page_io      | counter        | Number of File Space Header Pages read                                                                           |
| buffer_page_read_xdes                      | buffer_page_io      | counter        | Number of Extent Descriptor Pages read                                                                           |
| buffer_page_read_blob                      | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages read                                                                           |
| buffer_page_read_zblob                     | buffer_page_io      | counter        | Number of First Compressed BLOB Pages read                                                                       |
| buffer_page_read_zblob2                    | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages read                                                                  |
| buffer_page_read_other                     | buffer_page_io      | counter        | Number of other/unknown (old version of InnoDB) Pages read                                                       |
| buffer_page_written_index_leaf             | buffer_page_io      | counter        | Number of Index Leaf Pages written                                                                               |
| buffer_page_written_index_non_leaf         | buffer_page_io      | counter        | Number of Index Non-leaf Pages written                                                                           |
| buffer_page_written_index_ibuf_leaf        | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages written                                                                 |
| buffer_page_written_index_ibuf_non_leaf    | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages written                                                             |
| buffer_page_written_undo_log               | buffer_page_io      | counter        | Number of Undo Log Pages written                                                                                 |
| buffer_page_written_index_inode            | buffer_page_io      | counter        | Number of Index Inode Pages written                                                                              |
| buffer_page_written_ibuf_free_list         | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages written                                                                  |
| buffer_page_written_ibuf_bitmap            | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages written                                                                     |
| buffer_page_written_system_page            | buffer_page_io      | counter        | Number of System Pages written                                                                                   |
| buffer_page_written_trx_system             | buffer_page_io      | counter        | Number of Transaction System Pages written                                                                       |
| buffer_page_written_fsp_hdr                | buffer_page_io      | counter        | Number of File Space Header Pages written                                                                        |
| buffer_page_written_xdes                   | buffer_page_io      | counter        | Number of Extent Descriptor Pages written                                                                        |
| buffer_page_written_blob                   | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages written                                                                        |
| buffer_page_written_zblob                  | buffer_page_io      | counter        | Number of First Compressed BLOB Pages written                                                                    |
| buffer_page_written_zblob2                 | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages written                                                               |
| buffer_page_written_other                  | buffer_page_io      | counter        | Number of other/unknown (old version InnoDB) Pages written                                                       |
| os_data_reads                              | os                  | status_counter | Number of reads initiated (innodb_data_reads)                                                                    |
| os_data_writes                             | os                  | status_counter | Number of writes initiated (innodb_data_writes)                                                                  |
| os_data_fsyncs                             | os                  | status_counter | Number of fsync() calls (innodb_data_fsyncs)                                                                     |
| os_pending_reads                           | os                  | counter        | Number of reads pending                                                                                          |
| os_pending_writes                          | os                  | counter        | Number of writes pending                                                                                         |
| os_log_bytes_written                       | os                  | status_counter | Bytes of log written (innodb_os_log_written)                                                                     |
| os_log_fsyncs                              | os                  | status_counter | Number of fsync log writes (innodb_os_log_fsyncs)                                                                |
| os_log_pending_fsyncs                      | os                  | status_counter | Number of pending fsync write (innodb_os_log_pending_fsyncs)                                                     |
| os_log_pending_writes                      | os                  | status_counter | Number of pending log file writes (innodb_os_log_pending_writes)                                                 |
| trx_rw_commits                             | transaction         | counter        | Number of read-write transactions  committed                                                                     |
| trx_ro_commits                             | transaction         | counter        | Number of read-only transactions committed                                                                       |
| trx_nl_ro_commits                          | transaction         | counter        | Number of non-locking auto-commit read-only transactions committed                                               |
| trx_commits_insert_update                  | transaction         | counter        | Number of transactions committed with inserts and updates                                                        |
| trx_rollbacks                              | transaction         | counter        | Number of transactions rolled back                                                                               |
| trx_rollbacks_savepoint                    | transaction         | counter        | Number of transactions rolled back to savepoint                                                                  |
| trx_active_transactions                    | transaction         | counter        | Number of active transactions                                                                                    |
| trx_rseg_history_len                       | transaction         | value          | Length of the TRX_RSEG_HISTORY list                                                                              |
| trx_undo_slots_used                        | transaction         | counter        | Number of undo slots used                                                                                        |
| trx_undo_slots_cached                      | transaction         | counter        | Number of undo slots cached                                                                                      |
| trx_rseg_current_size                      | transaction         | value          | Current rollback segment size in pages                                                                           |
| purge_del_mark_records                     | purge               | counter        | Number of delete-marked rows purged                                                                              |
| purge_upd_exist_or_extern_records          | purge               | counter        | Number of purges on updates of existing records and updates on delete marked record with externally stored field |
| purge_invoked                              | purge               | counter        | Number of times purge was invoked                                                                                |
| purge_undo_log_pages                       | purge               | counter        | Number of undo log pages handled by the purge                                                                    |
| purge_dml_delay_usec                       | purge               | value          | Microseconds DML to be delayed due to purge lagging                                                              |
| purge_stop_count                           | purge               | value          | Number of times purge was stopped                                                                                |
| purge_resume_count                         | purge               | value          | Number of times purge was resumed                                                                                |
| log_checkpoints                            | recovery            | counter        | Number of checkpoints                                                                                            |
| log_lsn_last_flush                         | recovery            | value          | LSN of Last flush                                                                                                |
| log_lsn_last_checkpoint                    | recovery            | value          | LSN at last checkpoint                                                                                           |
| log_lsn_current                            | recovery            | value          | Current LSN value                                                                                                |
| log_lsn_checkpoint_age                     | recovery            | value          | Current LSN value minus LSN at last checkpoint                                                                   |
| log_lsn_buf_pool_oldest                    | recovery            | value          | The oldest modified block LSN in the buffer pool                                                                 |
| log_max_modified_age_async                 | recovery            | value          | Maximum LSN difference; when exceeded, start asynchronous preflush                                               |
| log_pending_log_flushes                    | recovery            | value          | Pending log flushes                                                                                              |
| log_pending_checkpoint_writes              | recovery            | value          | Pending checkpoints                                                                                              |
| log_num_log_io                             | recovery            | value          | Number of log I/Os                                                                                               |
| log_waits                                  | recovery            | status_counter | Number of log waits due to small log buffer (innodb_log_waits)                                                   |
| log_write_requests                         | recovery            | status_counter | Number of log write requests (innodb_log_write_requests)                                                         |
| log_writes                                 | recovery            | status_counter | Number of log writes (innodb_log_writes)                                                                         |
| log_padded                                 | recovery            | status_counter | Bytes of log padded for log write ahead                                                                          |
| compress_pages_compressed                  | compression         | counter        | Number of pages compressed                                                                                       |
| compress_pages_decompressed                | compression         | counter        | Number of pages decompressed                                                                                     |
| compression_pad_increments                 | compression         | counter        | Number of times padding is incremented to avoid compression failures                                             |
| compression_pad_decrements                 | compression         | counter        | Number of times padding is decremented due to good compressibility                                               |
| compress_saved                             | compression         | counter        | Number of bytes saved by page compression                                                                        |
| compress_pages_page_compressed             | compression         | counter        | Number of pages compressed by page compression                                                                   |
| compress_page_compressed_trim_op           | compression         | counter        | Number of TRIM operation performed by page compression                                                           |
| compress_pages_page_decompressed           | compression         | counter        | Number of pages decompressed by page compression                                                                 |
| compress_pages_page_compression_error      | compression         | counter        | Number of page compression errors                                                                                |
| compress_pages_encrypted                   | compression         | counter        | Number of pages encrypted                                                                                        |
| compress_pages_decrypted                   | compression         | counter        | Number of pages decrypted                                                                                        |
| index_page_splits                          | index               | counter        | Number of index page splits                                                                                      |
| index_page_merge_attempts                  | index               | counter        | Number of index page merge attempts                                                                              |
| index_page_merge_successful                | index               | counter        | Number of successful index page merges                                                                           |
| index_page_reorg_attempts                  | index               | counter        | Number of index page reorganization attempts                                                                     |
| index_page_reorg_successful                | index               | counter        | Number of successful index page reorganizations                                                                  |
| index_page_discards                        | index               | counter        | Number of index pages discarded                                                                                  |
| adaptive_hash_searches                     | adaptive_hash_index | status_counter | Number of successful searches using Adaptive Hash Index                                                          |
| adaptive_hash_searches_btree               | adaptive_hash_index | status_counter | Number of searches using B-tree on an index search                                                               |
| adaptive_hash_pages_added                  | adaptive_hash_index | counter        | Number of index pages on which the Adaptive Hash Index is built                                                  |
| adaptive_hash_pages_removed                | adaptive_hash_index | counter        | Number of index pages whose corresponding Adaptive Hash Index entries were removed                               |
| adaptive_hash_rows_added                   | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows added                                                                         |
| adaptive_hash_rows_removed                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows removed                                                                       |
| adaptive_hash_rows_deleted_no_hash_entry   | adaptive_hash_index | counter        | Number of rows deleted that did not have corresponding Adaptive Hash Index entries                               |
| adaptive_hash_rows_updated                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows updated                                                                       |
| file_num_open_files                        | file_system         | value          | Number of files currently open (innodb_num_open_files)                                                           |
| ibuf_merges_insert                         | change_buffer       | status_counter | Number of inserted records merged by change buffering                                                            |
| ibuf_merges_delete_mark                    | change_buffer       | status_counter | Number of deleted records merged by change buffering                                                             |
| ibuf_merges_delete                         | change_buffer       | status_counter | Number of purge records merged by change buffering                                                               |
| ibuf_merges_discard_insert                 | change_buffer       | status_counter | Number of insert merged operations discarded                                                                     |
| ibuf_merges_discard_delete_mark            | change_buffer       | status_counter | Number of deleted merged operations discarded                                                                    |
| ibuf_merges_discard_delete                 | change_buffer       | status_counter | Number of purge merged  operations discarded                                                                     |
| ibuf_merges                                | change_buffer       | status_counter | Number of change buffer merges                                                                                   |
| ibuf_size                                  | change_buffer       | status_counter | Change buffer size in pages                                                                                      |
| innodb_master_thread_sleeps                | server              | counter        | Number of times (seconds) master thread sleeps                                                                   |
| innodb_activity_count                      | server              | status_counter | Current server activity count                                                                                    |
| innodb_master_active_loops                 | server              | counter        | Number of times master thread performs its tasks when server is active                                           |
| innodb_master_idle_loops                   | server              | counter        | Number of times master thread performs its tasks when server is idle                                             |
| innodb_background_drop_table_usec          | server              | counter        | Time (in microseconds) spent to process drop table list                                                          |
| innodb_log_flush_usec                      | server              | counter        | Time (in microseconds) spent to flush log records                                                                |
| innodb_dict_lru_usec                       | server              | counter        | Time (in microseconds) spent to process DICT LRU list                                                            |
| innodb_dict_lru_count_active               | server              | counter        | Number of tables evicted from DICT LRU list in the active loop                                                   |
| innodb_dict_lru_count_idle                 | server              | counter        | Number of tables evicted from DICT LRU list in the idle loop                                                     |
| innodb_dblwr_writes                        | server              | status_counter | Number of doublewrite operations that have been performed (innodb_dblwr_writes)                                  |
| innodb_dblwr_pages_written                 | server              | status_counter | Number of pages that have been written for doublewrite operations (innodb_dblwr_pages_written)                   |
| innodb_page_size                           | server              | value          | InnoDB page size in bytes (innodb_page_size)                                                                     |
| innodb_rwlock_s_spin_waits                 | server              | status_counter | Number of rwlock spin waits due to shared latch request                                                          |
| innodb_rwlock_x_spin_waits                 | server              | status_counter | Number of rwlock spin waits due to exclusive latch request                                                       |
| innodb_rwlock_sx_spin_waits                | server              | status_counter | Number of rwlock spin waits due to sx latch request                                                              |
| innodb_rwlock_s_spin_rounds                | server              | status_counter | Number of rwlock spin loop rounds due to shared latch request                                                    |
| innodb_rwlock_x_spin_rounds                | server              | status_counter | Number of rwlock spin loop rounds due to exclusive latch request                                                 |
| innodb_rwlock_sx_spin_rounds               | server              | status_counter | Number of rwlock spin loop rounds due to sx latch request                                                        |
| innodb_rwlock_s_os_waits                   | server              | status_counter | Number of OS waits due to shared latch request                                                                   |
| innodb_rwlock_x_os_waits                   | server              | status_counter | Number of OS waits due to exclusive latch request                                                                |
| innodb_rwlock_sx_os_waits                  | server              | status_counter | Number of OS waits due to sx latch request                                                                       |
| dml_reads                                  | dml                 | status_counter | Number of rows read                                                                                              |
| dml_inserts                                | dml                 | status_counter | Number of rows inserted                                                                                          |
| dml_deletes                                | dml                 | status_counter | Number of rows deleted                                                                                           |
| dml_updates                                | dml                 | status_counter | Number of rows updated                                                                                           |
| dml_system_reads                           | dml                 | status_counter | Number of system rows read                                                                                       |
| dml_system_inserts                         | dml                 | status_counter | Number of system rows inserted                                                                                   |
| dml_system_deletes                         | dml                 | status_counter | Number of system rows deleted                                                                                    |
| dml_system_updates                         | dml                 | status_counter | Number of system rows updated                                                                                    |
| ddl_background_drop_indexes                | ddl                 | counter        | Number of indexes waiting to be dropped after failed index creation                                              |
| ddl_background_drop_tables                 | ddl                 | counter        | Number of tables in background drop table list                                                                   |
| ddl_online_create_index                    | ddl                 | counter        | Number of indexes being created online                                                                           |
| ddl_pending_alter_table                    | ddl                 | counter        | Number of ALTER TABLE, CREATE INDEX, DROP INDEX in progress                                                      |
| ddl_sort_file_alter_table                  | ddl                 | counter        | Number of sort files created during alter table                                                                  |
| ddl_log_file_alter_table                   | ddl                 | counter        | Number of log files created during alter table                                                                   |
| icp_attempts                               | icp                 | counter        | Number of attempts for index push-down condition checks                                                          |
| icp_no_match                               | icp                 | counter        | Index push-down condition does not match                                                                         |
| icp_out_of_range                           | icp                 | counter        | Index push-down condition out of range                                                                           |
| icp_match                                  | icp                 | counter        | Index push-down condition matches                                                                                |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
234 rows in set (0.001 sec)

From MariaDB 10.6

SELECT name,subsystem,type,comment FROM INFORMATION_SCHEMA.INNODB_METRICS;
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| name                                       | subsystem           | type           | comment                                                                                                          |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| metadata_table_handles_opened              | metadata            | counter        | Number of table handles opened                                                                                   |
| lock_deadlocks                             | lock                | value          | Number of deadlocks                                                                                              |
| lock_timeouts                              | lock                | value          | Number of lock timeouts                                                                                          |
| lock_rec_lock_waits                        | lock                | counter        | Number of times enqueued into record lock wait queue                                                             |
| lock_table_lock_waits                      | lock                | counter        | Number of times enqueued into table lock wait queue                                                              |
| lock_rec_lock_requests                     | lock                | counter        | Number of record locks requested                                                                                 |
| lock_rec_lock_created                      | lock                | counter        | Number of record locks created                                                                                   |
| lock_rec_lock_removed                      | lock                | counter        | Number of record locks removed from the lock queue                                                               |
| lock_rec_locks                             | lock                | counter        | Current number of record locks on tables                                                                         |
| lock_table_lock_created                    | lock                | counter        | Number of table locks created                                                                                    |
| lock_table_lock_removed                    | lock                | counter        | Number of table locks removed from the lock queue                                                                |
| lock_table_locks                           | lock                | counter        | Current number of table locks on tables                                                                          |
| lock_row_lock_current_waits                | lock                | status_counter | Number of row locks currently being waited for (innodb_row_lock_current_waits)                                   |
| lock_row_lock_time                         | lock                | status_counter | Time spent in acquiring row locks, in milliseconds (innodb_row_lock_time)                                        |
| lock_row_lock_time_max                     | lock                | value          | The maximum time to acquire a row lock, in milliseconds (innodb_row_lock_time_max)                               |
| lock_row_lock_waits                        | lock                | status_counter | Number of times a row lock had to be waited for (innodb_row_lock_waits)                                          |
| lock_row_lock_time_avg                     | lock                | value          | The average time to acquire a row lock, in milliseconds (innodb_row_lock_time_avg)                               |
| buffer_pool_size                           | server              | value          | Server buffer pool size (all buffer pools) in bytes                                                              |
| buffer_pool_reads                          | buffer              | status_counter | Number of reads directly from disk (innodb_buffer_pool_reads)                                                    |
| buffer_pool_read_requests                  | buffer              | status_counter | Number of logical read requests (innodb_buffer_pool_read_requests)                                               |
| buffer_pool_write_requests                 | buffer              | status_counter | Number of write requests (innodb_buffer_pool_write_requests)                                                     |
| buffer_pool_wait_free                      | buffer              | status_counter | Number of times waited for free buffer (innodb_buffer_pool_wait_free)                                            |
| buffer_pool_read_ahead                     | buffer              | status_counter | Number of pages read as read ahead (innodb_buffer_pool_read_ahead)                                               |
| buffer_pool_read_ahead_evicted             | buffer              | status_counter | Read-ahead pages evicted without being accessed (innodb_buffer_pool_read_ahead_evicted)                          |
| buffer_pool_pages_total                    | buffer              | value          | Total buffer pool size in pages (innodb_buffer_pool_pages_total)                                                 |
| buffer_pool_pages_misc                     | buffer              | value          | Buffer pages for misc use such as row locks or the adaptive hash index (innodb_buffer_pool_pages_misc)           |
| buffer_pool_pages_data                     | buffer              | value          | Buffer pages containing data (innodb_buffer_pool_pages_data)                                                     |
| buffer_pool_bytes_data                     | buffer              | value          | Buffer bytes containing data (innodb_buffer_pool_bytes_data)                                                     |
| buffer_pool_pages_dirty                    | buffer              | value          | Buffer pages currently dirty (innodb_buffer_pool_pages_dirty)                                                    |
| buffer_pool_bytes_dirty                    | buffer              | value          | Buffer bytes currently dirty (innodb_buffer_pool_bytes_dirty)                                                    |
| buffer_pool_pages_free                     | buffer              | value          | Buffer pages currently free (innodb_buffer_pool_pages_free)                                                      |
| buffer_pages_created                       | buffer              | status_counter | Number of pages created (innodb_pages_created)                                                                   |
| buffer_pages_written                       | buffer              | status_counter | Number of pages written (innodb_pages_written)                                                                   |
| buffer_index_pages_written                 | buffer              | status_counter | Number of index pages written (innodb_index_pages_written)                                                       |
| buffer_non_index_pages_written             | buffer              | status_counter | Number of non index pages written (innodb_non_index_pages_written)                                               |
| buffer_pages_read                          | buffer              | status_counter | Number of pages read (innodb_pages_read)                                                                         |
| buffer_index_sec_rec_cluster_reads         | buffer              | status_counter | Number of secondary record reads triggered cluster read                                                          |
| buffer_index_sec_rec_cluster_reads_avoided | buffer              | status_counter | Number of secondary record reads avoided triggering cluster read                                                 |
| buffer_data_reads                          | buffer              | status_counter | Amount of data read in bytes (innodb_data_reads)                                                                 |
| buffer_data_written                        | buffer              | status_counter | Amount of data written in bytes (innodb_data_written)                                                            |
| buffer_flush_batch_scanned                 | buffer              | set_owner      | Total pages scanned as part of flush batch                                                                       |
| buffer_flush_batch_num_scan                | buffer              | set_member     | Number of times buffer flush list flush is called                                                                |
| buffer_flush_batch_scanned_per_call        | buffer              | set_member     | Pages scanned per flush batch scan                                                                               |
| buffer_flush_batch_total_pages             | buffer              | set_owner      | Total pages flushed as part of flush batch                                                                       |
| buffer_flush_batches                       | buffer              | set_member     | Number of flush batches                                                                                          |
| buffer_flush_batch_pages                   | buffer              | set_member     | Pages queued as a flush batch                                                                                    |
| buffer_flush_neighbor_total_pages          | buffer              | set_owner      | Total neighbors flushed as part of neighbor flush                                                                |
| buffer_flush_neighbor                      | buffer              | set_member     | Number of times neighbors flushing is invoked                                                                    |
| buffer_flush_neighbor_pages                | buffer              | set_member     | Pages queued as a neighbor batch                                                                                 |
| buffer_flush_n_to_flush_requested          | buffer              | counter        | Number of pages requested for flushing.                                                                          |
| buffer_flush_n_to_flush_by_age             | buffer              | counter        | Number of pages target by LSN Age for flushing.                                                                  |
| buffer_flush_adaptive_avg_time             | buffer              | counter        | Avg time (ms) spent for adaptive flushing recently.                                                              |
| buffer_flush_adaptive_avg_pass             | buffer              | counter        | Number of adaptive flushes passed during the recent Avg period.                                                  |
| buffer_LRU_get_free_loops                  | buffer              | counter        | Total loops in LRU get free.                                                                                     |
| buffer_LRU_get_free_waits                  | buffer              | counter        | Total sleep waits in LRU get free.                                                                               |
| buffer_flush_avg_page_rate                 | buffer              | counter        | Average number of pages at which flushing is happening                                                           |
| buffer_flush_lsn_avg_rate                  | buffer              | counter        | Average redo generation rate                                                                                     |
| buffer_flush_pct_for_dirty                 | buffer              | counter        | Percent of IO capacity used to avoid max dirty page limit                                                        |
| buffer_flush_pct_for_lsn                   | buffer              | counter        | Percent of IO capacity used to avoid reusable redo space limit                                                   |
| buffer_flush_sync_waits                    | buffer              | counter        | Number of times a wait happens due to sync flushing                                                              |
| buffer_flush_adaptive_total_pages          | buffer              | set_owner      | Total pages flushed as part of adaptive flushing                                                                 |
| buffer_flush_adaptive                      | buffer              | set_member     | Number of adaptive batches                                                                                       |
| buffer_flush_adaptive_pages                | buffer              | set_member     | Pages queued as an adaptive batch                                                                                |
| buffer_flush_sync_total_pages              | buffer              | set_owner      | Total pages flushed as part of sync batches                                                                      |
| buffer_flush_sync                          | buffer              | set_member     | Number of sync batches                                                                                           |
| buffer_flush_sync_pages                    | buffer              | set_member     | Pages queued as a sync batch                                                                                     |
| buffer_flush_background_total_pages        | buffer              | set_owner      | Total pages flushed as part of background batches                                                                |
| buffer_flush_background                    | buffer              | set_member     | Number of background batches                                                                                     |
| buffer_flush_background_pages              | buffer              | set_member     | Pages queued as a background batch                                                                               |
| buffer_LRU_batch_scanned                   | buffer              | set_owner      | Total pages scanned as part of LRU batch                                                                         |
| buffer_LRU_batch_num_scan                  | buffer              | set_member     | Number of times LRU batch is called                                                                              |
| buffer_LRU_batch_scanned_per_call          | buffer              | set_member     | Pages scanned per LRU batch call                                                                                 |
| buffer_LRU_batch_flush_total_pages         | buffer              | status_counter | Total pages flushed as part of LRU batches                                                                       |
| buffer_LRU_batch_evict_total_pages         | buffer              | status_counter | Total pages evicted as part of LRU batches                                                                       |
| buffer_LRU_single_flush_failure_count      | Buffer              | counter        | Number of times attempt to flush a single page from LRU failed                                                   |
| buffer_LRU_get_free_search                 | Buffer              | counter        | Number of searches performed for a clean page                                                                    |
| buffer_LRU_search_scanned                  | buffer              | set_owner      | Total pages scanned as part of LRU search                                                                        |
| buffer_LRU_search_num_scan                 | buffer              | set_member     | Number of times LRU search is performed                                                                          |
| buffer_LRU_search_scanned_per_call         | buffer              | set_member     | Page scanned per single LRU search                                                                               |
| buffer_LRU_unzip_search_scanned            | buffer              | set_owner      | Total pages scanned as part of LRU unzip search                                                                  |
| buffer_LRU_unzip_search_num_scan           | buffer              | set_member     | Number of times LRU unzip search is performed                                                                    |
| buffer_LRU_unzip_search_scanned_per_call   | buffer              | set_member     | Page scanned per single LRU unzip search                                                                         |
| buffer_page_read_index_leaf                | buffer_page_io      | counter        | Number of Index Leaf Pages read                                                                                  |
| buffer_page_read_index_non_leaf            | buffer_page_io      | counter        | Number of Index Non-leaf Pages read                                                                              |
| buffer_page_read_index_ibuf_leaf           | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages read                                                                    |
| buffer_page_read_index_ibuf_non_leaf       | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages read                                                                |
| buffer_page_read_undo_log                  | buffer_page_io      | counter        | Number of Undo Log Pages read                                                                                    |
| buffer_page_read_index_inode               | buffer_page_io      | counter        | Number of Index Inode Pages read                                                                                 |
| buffer_page_read_ibuf_free_list            | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages read                                                                     |
| buffer_page_read_ibuf_bitmap               | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages read                                                                        |
| buffer_page_read_system_page               | buffer_page_io      | counter        | Number of System Pages read                                                                                      |
| buffer_page_read_trx_system                | buffer_page_io      | counter        | Number of Transaction System Pages read                                                                          |
| buffer_page_read_fsp_hdr                   | buffer_page_io      | counter        | Number of File Space Header Pages read                                                                           |
| buffer_page_read_xdes                      | buffer_page_io      | counter        | Number of Extent Descriptor Pages read                                                                           |
| buffer_page_read_blob                      | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages read                                                                           |
| buffer_page_read_zblob                     | buffer_page_io      | counter        | Number of First Compressed BLOB Pages read                                                                       |
| buffer_page_read_zblob2                    | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages read                                                                  |
| buffer_page_read_other                     | buffer_page_io      | counter        | Number of other/unknown (old version of InnoDB) Pages read                                                       |
| buffer_page_written_index_leaf             | buffer_page_io      | counter        | Number of Index Leaf Pages written                                                                               |
| buffer_page_written_index_non_leaf         | buffer_page_io      | counter        | Number of Index Non-leaf Pages written                                                                           |
| buffer_page_written_index_ibuf_leaf        | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages written                                                                 |
| buffer_page_written_index_ibuf_non_leaf    | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages written                                                             |
| buffer_page_written_undo_log               | buffer_page_io      | counter        | Number of Undo Log Pages written                                                                                 |
| buffer_page_written_index_inode            | buffer_page_io      | counter        | Number of Index Inode Pages written                                                                              |
| buffer_page_written_ibuf_free_list         | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages written                                                                  |
| buffer_page_written_ibuf_bitmap            | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages written                                                                     |
| buffer_page_written_system_page            | buffer_page_io      | counter        | Number of System Pages written                                                                                   |
| buffer_page_written_trx_system             | buffer_page_io      | counter        | Number of Transaction System Pages written                                                                       |
| buffer_page_written_fsp_hdr                | buffer_page_io      | counter        | Number of File Space Header Pages written                                                                        |
| buffer_page_written_xdes                   | buffer_page_io      | counter        | Number of Extent Descriptor Pages written                                                                        |
| buffer_page_written_blob                   | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages written                                                                        |
| buffer_page_written_zblob                  | buffer_page_io      | counter        | Number of First Compressed BLOB Pages written                                                                    |
| buffer_page_written_zblob2                 | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages written                                                               |
| buffer_page_written_other                  | buffer_page_io      | counter        | Number of other/unknown (old version InnoDB) Pages written                                                       |
| os_data_reads                              | os                  | status_counter | Number of reads initiated (innodb_data_reads)                                                                    |
| os_data_writes                             | os                  | status_counter | Number of writes initiated (innodb_data_writes)                                                                  |
| os_data_fsyncs                             | os                  | status_counter | Number of fsync() calls (innodb_data_fsyncs)                                                                     |
| os_pending_reads                           | os                  | counter        | Number of reads pending                                                                                          |
| os_pending_writes                          | os                  | counter        | Number of writes pending                                                                                         |
| os_log_bytes_written                       | os                  | status_counter | Bytes of log written (innodb_os_log_written)                                                                     |
| os_log_fsyncs                              | os                  | status_counter | Number of fsync log writes (innodb_os_log_fsyncs)                                                                |
| os_log_pending_fsyncs                      | os                  | status_counter | Number of pending fsync write (innodb_os_log_pending_fsyncs)                                                     |
| os_log_pending_writes                      | os                  | status_counter | Number of pending log file writes (innodb_os_log_pending_writes)                                                 |
| trx_rw_commits                             | transaction         | counter        | Number of read-write transactions  committed                                                                     |
| trx_ro_commits                             | transaction         | counter        | Number of read-only transactions committed                                                                       |
| trx_nl_ro_commits                          | transaction         | counter        | Number of non-locking auto-commit read-only transactions committed                                               |
| trx_commits_insert_update                  | transaction         | counter        | Number of transactions committed with inserts and updates                                                        |
| trx_rollbacks                              | transaction         | counter        | Number of transactions rolled back                                                                               |
| trx_rollbacks_savepoint                    | transaction         | counter        | Number of transactions rolled back to savepoint                                                                  |
| trx_rseg_history_len                       | transaction         | value          | Length of the TRX_RSEG_HISTORY list                                                                              |
| trx_undo_slots_used                        | transaction         | counter        | Number of undo slots used                                                                                        |
| trx_undo_slots_cached                      | transaction         | counter        | Number of undo slots cached                                                                                      |
| trx_rseg_current_size                      | transaction         | value          | Current rollback segment size in pages                                                                           |
| purge_del_mark_records                     | purge               | counter        | Number of delete-marked rows purged                                                                              |
| purge_upd_exist_or_extern_records          | purge               | counter        | Number of purges on updates of existing records and updates on delete marked record with externally stored field |
| purge_invoked                              | purge               | counter        | Number of times purge was invoked                                                                                |
| purge_undo_log_pages                       | purge               | counter        | Number of undo log pages handled by the purge                                                                    |
| purge_dml_delay_usec                       | purge               | value          | Microseconds DML to be delayed due to purge lagging                                                              |
| purge_stop_count                           | purge               | value          | Number of times purge was stopped                                                                                |
| purge_resume_count                         | purge               | value          | Number of times purge was resumed                                                                                |
| log_checkpoints                            | recovery            | counter        | Number of checkpoints                                                                                            |
| log_lsn_last_flush                         | recovery            | value          | LSN of Last flush                                                                                                |
| log_lsn_last_checkpoint                    | recovery            | value          | LSN at last checkpoint                                                                                           |
| log_lsn_current                            | recovery            | value          | Current LSN value                                                                                                |
| log_lsn_checkpoint_age                     | recovery            | value          | Current LSN value minus LSN at last checkpoint                                                                   |
| log_lsn_buf_pool_oldest                    | recovery            | value          | The oldest modified block LSN in the buffer pool                                                                 |
| log_max_modified_age_async                 | recovery            | value          | Maximum LSN difference; when exceeded, start asynchronous preflush                                               |
| log_pending_log_flushes                    | recovery            | value          | Pending log flushes                                                                                              |
| log_pending_checkpoint_writes              | recovery            | value          | Pending checkpoints                                                                                              |
| log_num_log_io                             | recovery            | value          | Number of log I/Os                                                                                               |
| log_waits                                  | recovery            | status_counter | Number of log waits due to small log buffer (innodb_log_waits)                                                   |
| log_write_requests                         | recovery            | status_counter | Number of log write requests (innodb_log_write_requests)                                                         |
| log_writes                                 | recovery            | status_counter | Number of log writes (innodb_log_writes)                                                                         |
| log_padded                                 | recovery            | status_counter | Bytes of log padded for log write ahead                                                                          |
| compress_pages_compressed                  | compression         | counter        | Number of pages compressed                                                                                       |
| compress_pages_decompressed                | compression         | counter        | Number of pages decompressed                                                                                     |
| compression_pad_increments                 | compression         | counter        | Number of times padding is incremented to avoid compression failures                                             |
| compression_pad_decrements                 | compression         | counter        | Number of times padding is decremented due to good compressibility                                               |
| compress_saved                             | compression         | counter        | Number of bytes saved by page compression                                                                        |
| compress_pages_page_compressed             | compression         | counter        | Number of pages compressed by page compression                                                                   |
| compress_page_compressed_trim_op           | compression         | counter        | Number of TRIM operation performed by page compression                                                           |
| compress_pages_page_decompressed           | compression         | counter        | Number of pages decompressed by page compression                                                                 |
| compress_pages_page_compression_error      | compression         | counter        | Number of page compression errors                                                                                |
| compress_pages_encrypted                   | compression         | counter        | Number of pages encrypted                                                                                        |
| compress_pages_decrypted                   | compression         | counter        | Number of pages decrypted                                                                                        |
| index_page_splits                          | index               | counter        | Number of index page splits                                                                                      |
| index_page_merge_attempts                  | index               | counter        | Number of index page merge attempts                                                                              |
| index_page_merge_successful                | index               | counter        | Number of successful index page merges                                                                           |
| index_page_reorg_attempts                  | index               | counter        | Number of index page reorganization attempts                                                                     |
| index_page_reorg_successful                | index               | counter        | Number of successful index page reorganizations                                                                  |
| index_page_discards                        | index               | counter        | Number of index pages discarded                                                                                  |
| adaptive_hash_searches                     | adaptive_hash_index | status_counter | Number of successful searches using Adaptive Hash Index                                                          |
| adaptive_hash_searches_btree               | adaptive_hash_index | status_counter | Number of searches using B-tree on an index search                                                               |
| adaptive_hash_pages_added                  | adaptive_hash_index | counter        | Number of index pages on which the Adaptive Hash Index is built                                                  |
| adaptive_hash_pages_removed                | adaptive_hash_index | counter        | Number of index pages whose corresponding Adaptive Hash Index entries were removed                               |
| adaptive_hash_rows_added                   | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows added                                                                         |
| adaptive_hash_rows_removed                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows removed                                                                       |
| adaptive_hash_rows_deleted_no_hash_entry   | adaptive_hash_index | counter        | Number of rows deleted that did not have corresponding Adaptive Hash Index entries                               |
| adaptive_hash_rows_updated                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows updated                                                                       |
| file_num_open_files                        | file_system         | value          | Number of files currently open (innodb_num_open_files)                                                           |
| ibuf_merges_insert                         | change_buffer       | status_counter | Number of inserted records merged by change buffering                                                            |
| ibuf_merges_delete_mark                    | change_buffer       | status_counter | Number of deleted records merged by change buffering                                                             |
| ibuf_merges_delete                         | change_buffer       | status_counter | Number of purge records merged by change buffering                                                               |
| ibuf_merges_discard_insert                 | change_buffer       | status_counter | Number of insert merged operations discarded                                                                     |
| ibuf_merges_discard_delete_mark            | change_buffer       | status_counter | Number of deleted merged operations discarded                                                                    |
| ibuf_merges_discard_delete                 | change_buffer       | status_counter | Number of purge merged  operations discarded                                                                     |
| ibuf_merges                                | change_buffer       | status_counter | Number of change buffer merges                                                                                   |
| ibuf_size                                  | change_buffer       | status_counter | Change buffer size in pages                                                                                      |
| innodb_master_thread_sleeps                | server              | counter        | Number of times (seconds) master thread sleeps                                                                   |
| innodb_activity_count                      | server              | status_counter | Current server activity count                                                                                    |
| innodb_master_active_loops                 | server              | counter        | Number of times master thread performs its tasks when server is active                                           |
| innodb_master_idle_loops                   | server              | counter        | Number of times master thread performs its tasks when server is idle                                             |
| innodb_log_flush_usec                      | server              | counter        | Time (in microseconds) spent to flush log records                                                                |
| innodb_dict_lru_usec                       | server              | counter        | Time (in microseconds) spent to process DICT LRU list                                                            |
| innodb_dict_lru_count_active               | server              | counter        | Number of tables evicted from DICT LRU list in the active loop                                                   |
| innodb_dict_lru_count_idle                 | server              | counter        | Number of tables evicted from DICT LRU list in the idle loop                                                     |
| innodb_dblwr_writes                        | server              | status_counter | Number of doublewrite operations that have been performed (innodb_dblwr_writes)                                  |
| innodb_dblwr_pages_written                 | server              | status_counter | Number of pages that have been written for doublewrite operations (innodb_dblwr_pages_written)                   |
| innodb_page_size                           | server              | value          | InnoDB page size in bytes (innodb_page_size)                                                                     |
| dml_reads                                  | dml                 | status_counter | Number of rows read                                                                                              |
| dml_inserts                                | dml                 | status_counter | Number of rows inserted                                                                                          |
| dml_deletes                                | dml                 | status_counter | Number of rows deleted                                                                                           |
| dml_updates                                | dml                 | status_counter | Number of rows updated                                                                                           |
| dml_system_reads                           | dml                 | status_counter | Number of system rows read                                                                                       |
| dml_system_inserts                         | dml                 | status_counter | Number of system rows inserted                                                                                   |
| dml_system_deletes                         | dml                 | status_counter | Number of system rows deleted                                                                                    |
| dml_system_updates                         | dml                 | status_counter | Number of system rows updated                                                                                    |
| ddl_background_drop_indexes                | ddl                 | counter        | Number of indexes waiting to be dropped after failed index creation                                              |
| ddl_online_create_index                    | ddl                 | counter        | Number of indexes being created online                                                                           |
| ddl_pending_alter_table                    | ddl                 | counter        | Number of ALTER TABLE, CREATE INDEX, DROP INDEX in progress                                                      |
| ddl_sort_file_alter_table                  | ddl                 | counter        | Number of sort files created during alter table                                                                  |
| ddl_log_file_alter_table                   | ddl                 | counter        | Number of log files created during alter table                                                                   |
| icp_attempts                               | icp                 | counter        | Number of attempts for index push-down condition checks                                                          |
| icp_no_match                               | icp                 | counter        | Index push-down condition does not match                                                                         |
| icp_out_of_range                           | icp                 | counter        | Index push-down condition out of range                                                                           |
| icp_match                                  | icp                 | counter        | Index push-down condition matches                                                                                |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
216 rows in set (0.000 sec)

1.1.2.9.1.1.1.20 Information Schema INNODB_MUTEXES Table

The INNODB_MUTEXES table monitors mutex and rw locks waits. It has the following columns:

ColumnDescription
NAMEName of the lock, as it appears in the source code.
CREATE_FILEFile name of the mutex implementation.
CREATE_LINELine number of the mutex implementation.
OS_WAITSHow many times the mutex occurred.

The CREATE_FILE and CREATE_LINE columns depend on the InnoDB/XtraDB version.

Note that since MariaDB 10.2.2, the table has only been providing information about rw_lock_t, not any mutexes. From MariaDB 10.2.2 until MariaDB 10.2.32, MariaDB 10.3.23, MariaDB 10.4.13 and MariaDB 10.5.1, the NAME column was not populated (MDEV-21636).

The SHOW ENGINE INNODB STATUS statement provides similar information.

Examples

SELECT * FROM INNODB_MUTEXES;
+------------------------------+---------------------+-------------+----------+
| NAME                         | CREATE_FILE         | CREATE_LINE | OS_WAITS |
+------------------------------+---------------------+-------------+----------+
| &dict_sys->mutex             | dict0dict.cc        |         989 |        2 |
| &buf_pool->flush_state_mutex | buf0buf.cc          |        1388 |        1 |
| &log_sys->checkpoint_lock    | log0log.cc          |        1014 |        2 |
| &block->lock                 | combined buf0buf.cc |        1120 |        1 |
+------------------------------+---------------------+-------------+----------+

1.1.2.9.1.1.1.21 Information Schema INNODB_SYS_COLUMNS Table

The Information Schema INNODB_SYS_COLUMNS table contains information about InnoDB fields.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
TABLE_IDTable identifier, matching the value from INNODB_SYS_TABLES.TABLE_ID.
NAMEColumn name.
POSOrdinal position of the column in the table, starting from 0. This value is adjusted when columns are added or removed.
MTYPENumeric column type identifier, (see the table below for an explanation of its values).
PRTYPEBinary value of the InnoDB precise type, representing the data type, character set code and nullability.
LENColumn length. For multi-byte character sets, represents the length in bytes.

The column MTYPE uses a numeric column type identifier, which has the following values:

Column Type IdentifierDescription
1VARCHAR
2CHAR
3FIXBINARY
4BINARY
5BLOB
6INT
7SYS_CHILD
8SYS
9FLOAT
10DOUBLE
11DECIMAL
12VARMYSQL
13MYSQL

Example

SELECT * FROM information_schema.INNODB_SYS_COLUMNS LIMIT 3\G
*************************** 1. row ***************************
TABLE_ID: 11
    NAME: ID
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
     LEN: 0
*************************** 2. row ***************************
TABLE_ID: 11
    NAME: FOR_NAME 
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
    LEN: 0
*************************** 3. row ***************************
TABLE_ID: 11
    NAME: REF_NAME 
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
     LEN: 0
3 rows in set (0.00 sec)

1.1.2.9.1.1.1.22 Information Schema INNODB_SYS_DATAFILES Table

MariaDB until 10.5

The INNODB_SYS_DATAFILES table was added in MariaDB 10.0.4, and removed in MariaDB 10.6.0.

The Information Schema INNODB_SYS_DATAFILES table contains information about InnoDB datafile paths. It was intended to provide metadata for tablespaces inside InnoDB tables, which was never implemented in MariaDB and was removed in MariaDB 10.6. The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
SPACENumeric tablespace. Matches the INNODB_SYS_TABLES.SPACE value.
PATHTablespace datafile path.

Example

SELECT * FROM INNODB_SYS_DATAFILES;
+-------+--------------------------------+
| SPACE | PATH                           |
+-------+--------------------------------+
|    19 | ./test/t2.ibd                  |
|    20 | ./test/t3.ibd                  |
...
|    68 | ./test/animals.ibd             |
|    69 | ./test/animal_count.ibd        |
|    70 | ./test/t.ibd                   |
+-------+--------------------------------+

1.1.2.9.1.1.1.23 Information Schema INNODB_SYS_FIELDS Table

The Information Schema INNODB_SYS_FIELDS table contains information about fields that are part of an InnoDB index.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
INDEX_IDIndex identifier, matching the value from INNODB_SYS_INDEXES.INDEX_ID.
NAMEField name, matching the value from INNODB_SYS_COLUMNS.NAME.
POSOrdinal position of the field within the index, starting from 0. This is adjusted as columns are removed.

Example

SELECT * FROM information_schema.INNODB_SYS_FIELDS LIMIT 3\G
*************************** 1. row ***************************
INDEX_ID: 11
    NAME: ID
     POS: 0
*************************** 2. row ***************************
INDEX_ID: 12
    NAME: FOR_NAME 
     POS: 0
*************************** 3. row ***************************
INDEX_ID: 13
    NAME: REF_NAME 
     POS: 0
3 rows in set (0.00 sec)

1.1.2.9.1.1.1.24 Information Schema INNODB_SYS_FOREIGN Table

The Information Schema INNODB_SYS_FOREIGN table contains information about InnoDB foreign keys.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
IDDatabase name and foreign key name.
FOR_NAMEDatabase and table name of the foreign key child.
REF_NAMEDatabase and table name of the foreign key parent.
N_COLSNumber of foreign key index columns.
TYPEBit flag providing information about the foreign key.

The TYPE column provides a bit flag with information about the foreign key. This information is OR'ed together to read:

Bit FlagDescription
1ON DELETE CASCADE
2ON UPDATE SET NULL
4ON UPDATE CASCADE
8ON UPDATE SET NULL
16ON DELETE NO ACTION
32ON UPDATE NO ACTION

Example

SELECT * FROM INNODB_SYS_FOREIGN\G
*************************** 1. row ***************************
      ID: mysql/innodb_index_stats_ibfk_1
FOR_NAME: mysql/innodb_index_stats
REF_NAME: mysql/innodb_table_stats
  N_COLS: 2
    TYPE: 0
...

1.1.2.9.1.1.1.25 Information Schema INNODB_SYS_FOREIGN_COLS Table

The Information Schema INNODB_SYS_FOREIGN_COLS table contains information about InnoDB foreign key columns.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
IDForeign key index associated with this column, matching the INNODB_SYS_FOREIGN.ID field.
FOR_COL_NAMEChild column name.
REF_COL_NAMEParent column name.
POSOrdinal position of the column in the table, starting from 0.

1.1.2.9.1.1.1.26 Information Schema INNODB_SYS_INDEXES Table

The Information Schema INNODB_SYS_INDEXES table contains information about InnoDB indexes.

The PROCESS privilege is required to view the table.

It has the following columns:

FieldTypeNullKeyDefaultDescription
INDEX_IDbigint(21) unsignedNO0A unique index identifier.
NAMEvarchar(64)NOIndex name, lowercase for all user-created indexes, or uppercase for implicitly-created indexes; PRIMARY (primary key), GEN_CLUST_INDEX (index representing primary key where there isn't one), ID_IND, FOR_IND (validating foreign key constraint) , REF_IND.
TABLE_IDbigint(21) unsignedNO0Table identifier, matching the value from INNODB_SYS_TABLES.TABLE_ID.
TYPEint(11)NO0Numeric type identifier; one of 0 (secondary index), 1 (clustered index), 2 (unique index), 3 (primary index), 32 (full-text index).
N_FIELDSint(11)NO0Number of columns in the index. GEN_CLUST_INDEX's have a value of 0 as the index is not based on an actual column in the table.
PAGE_NOint(11)NO0Index B-tree's root page number. -1 (unused) for full-text indexes, as they are laid out over several auxiliary tables.
SPACEint(11)NO0Tablespace identifier where the index resides. 0 represents the InnoDB system tablespace, while any other value represents a table created in file-per-table mode (see the innodb_file_per_table system variable). Remains unchanged after a TRUNCATE TABLE statement, and not necessarily unique.
MERGE_THRESHOLDint(11)NO0

Example

SELECT * FROM information_schema.INNODB_SYS_INDEXES LIMIT 3\G
*************************** 1. row ***************************
       INDEX_ID: 11
           NAME: ID_IND
       TABLE_ID: 11
           TYPE: 3
       N_FIELDS: 1
        PAGE_NO: 302
          SPACE: 0
MERGE_THRESHOLD: 50
*************************** 2. row ***************************
       INDEX_ID: 12
           NAME: FOR_IND
       TABLE_ID: 11
           TYPE: 0
       N_FIELDS: 1
        PAGE_NO: 303
          SPACE: 0
MERGE_THRESHOLD: 50
*************************** 3. row ***************************
       INDEX_ID: 13
           NAME: REF_IND
       TABLE_ID: 11
           TYPE: 3
       N_FIELDS: 1
        PAGE_NO: 304
          SPACE: 0
MERGE_THRESHOLD: 50
3 rows in set (0.00 sec)

1.1.2.9.1.1.1.27 Information Schema INNODB_SYS_SEMAPHORE_WAITS Table

The Information Schema INNODB_SYS_SEMAPHORE_WAITS table is meant to contain information about current semaphore waits. At present it is not correctly populated. See MDEV-21330.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
THREAD_IDThread id waiting for semaphore
OBJECT_NAMESemaphore name
FILEFile name where semaphore was requested
LINELine number on above file
WAIT_TIMEWait time
WAIT_OBJECT
WAIT_TYPEObject type (mutex, rw-lock)
HOLDER_THREAD_IDHolder thread id
HOLDER_FILEFile name where semaphore was acquired
HOLDER_LINELine number for above
CREATED_FILECreation file name
CREATED_LINELine number for above
WRITER_THREADLast write request thread id
RESERVATION_MODEReservation mode (shared, exclusive)
READERSNumber of readers if only shared mode
WAITERS_FLAGFlags
LOCK_WORDLock word (for developers)
LAST_READER_FILERemoved
LAST_READER_LINERemoved
LAST_WRITER_FILELast writer file name
LAST_WRITER_LINEAbove line number
OS_WAIT_COUNTWait count

1.1.2.9.1.1.1.28 Information Schema INNODB_SYS_TABLES Table

The Information Schema INNODB_SYS_TABLES table contains information about InnoDB tables.

The PROCESS privilege is required to view the table.

It has the following columns:

FieldTypeNullKeyDefaultDescription
TABLE_IDbigint(21) unsignedNO0Unique InnoDB table identifier.
NAMEvarchar(655)NODatabase and table name, or the uppercase InnoDB system table name.
FLAGint(11)NO0See Flag below
N_COLSint(11) unsigned (>= MariaDB 10.5)
int(11) (<= MariaDB 10.4)
NO0Number of columns in the table.
SPACEint(11) unsigned (>= MariaDB 10.5)
int(11) (<= MariaDB 10.4)
NO0Tablespace identifier where the index resides. 0 represents the InnoDB system tablespace, while any other value represents a table created in file-per-table mode (see the innodb_file_per_table system variable). Remains unchanged after a TRUNCATE TABLE statement.
FILE_FORMATvarchar(10)YESNULLInnoDB file format (Antelope or Barracuda). Removed in MariaDB 10.3.
ROW_FORMATenum('Redundant', 'Compact', 'Compressed', 'Dynamic') (>= MariaDB 10.5)
varchar(12) (<= MariaDB 10.4)
YESNULLInnoDB storage format (Compact, Redundant, Dynamic, or Compressed).
ZIP_PAGE_SIZEint(11) unsignedNO0For Compressed tables, the zipped page size.
SPACE_TYPEenum('Single','System') (>= MariaDB 10.5)
varchar(10) (<= MariaDB 10.4)
YESNULL

Flag

The flag field returns the dict_table_t::flags that correspond to the data dictionary record.

BitDescription
0Set if ROW_FORMAT is not REDUNDANT.
1 to 40, except for ROW_FORMAT=COMPRESSED, where they will determine the KEY_BLOCK_SIZE (the compressed page size).
5Set for ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED.
6Set if the DATA DIRECTORY attribute was present when the table was originally created.
7Set if the page_compressed attribute is present.
8 to 11Determine the page_compression_level.
12 13Normally 00, but 11 for "no-rollback tables" (MariaDB 10.3 CREATE SEQUENCE). In MariaDB 10.1, these bits could be 01 or 10 for ATOMIC_WRITES=ON or ATOMIC_WRITES=OFF.

Note that the table flags returned here are not the same as tablespace flags (FSP_SPACE_FLAGS).

Example

SELECT * FROM information_schema.INNODB_SYS_TABLES LIMIT 2\G
*************************** 1. row ***************************
     TABLE_ID: 14
         NAME: SYS_DATAFILES
         FLAG: 0
       N_COLS: 5
        SPACE: 0
  FILE_FORMAT: Antelope
   ROW_FORMAT: Redundant
ZIP_PAGE_SIZE: 0
   SPACE_TYPE: System
*************************** 2. row ***************************
     TABLE_ID: 11
         NAME: SYS_FOREIGN
         FLAG: 0
       N_COLS: 7
        SPACE: 0
  FILE_FORMAT: Antelope
   ROW_FORMAT: Redundant
ZIP_PAGE_SIZE: 0
   SPACE_TYPE: System
2 rows in set (0.00 sec)

See Also

1.1.2.9.1.1.1.29 Information Schema INNODB_SYS_TABLESPACES Table

The Information Schema INNODB_SYS_TABLESPACES table contains information about InnoDB tablespaces. Until MariaDB 10.5 it was based on the internal SYS_TABLESPACES table. This internal table was removed in MariaDB 10.6.0, so this Information Schema table has been repurposed to directly reflect the filesystem (fil_system.space_list).

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACEUnique InnoDB tablespace identifier.
NAMEDatabase and table name separated by a backslash, or the uppercase InnoDB system table name.
FLAG1 if a DATA DIRECTORY option has been specified in CREATE TABLE, otherwise 0.
FILE_FORMATInnoDB file format.
ROW_FORMATInnoDB storage format used for this tablespace. If the Antelope file format is used, this value is always Compact or Redundant.
PAGE_SIZEPage size in bytes for this tablespace. Until MariaDB 10.5.0, this was the value of the innodb_page_size variable. From MariaDB 10.6.0, contains the physical page size of a page (previously ZIP_PAGE_SIZE).
ZIP_PAGE_SIZEZip page size for this tablespace. Removed in MariaDB 10.6.0.
SPACE_TYPETablespace type. Can be General for general tablespaces or Single for file-per-table tablespaces. Introduced MariaDB 10.2.1. Removed MariaDB 10.5.0.
FS_BLOCK_SIZEFile system block size. Introduced MariaDB 10.2.1.
FILE_SIZEMaximum size of the file, uncompressed. Introduced MariaDB 10.2.1.
ALLOCATED_SIZEActual size of the file as per space allocated on disk. Introduced MariaDB 10.2.1.
FILENAMETablespace datafile path, previously part of the INNODB_SYS_DATAFILES table. Added in MariaDB 10.6.0.

Examples

MariaDB 10.4:

DESC information_schema.innodb_sys_tablespaces;
+----------------+---------------------+------+-----+---------+-------+
| Field          | Type                | Null | Key | Default | Extra |
+----------------+---------------------+------+-----+---------+-------+
| SPACE          | int(11) unsigned    | NO   |     | 0       |       |
| NAME           | varchar(655)        | NO   |     |         |       |
| FLAG           | int(11) unsigned    | NO   |     | 0       |       |
| FILE_FORMAT    | varchar(10)         | YES  |     | NULL    |       |
| ROW_FORMAT     | varchar(22)         | YES  |     | NULL    |       |
| PAGE_SIZE      | int(11) unsigned    | NO   |     | 0       |       |
| ZIP_PAGE_SIZE  | int(11) unsigned    | NO   |     | 0       |       |
| SPACE_TYPE     | varchar(10)         | YES  |     | NULL    |       |
| FS_BLOCK_SIZE  | int(11) unsigned    | NO   |     | 0       |       |
| FILE_SIZE      | bigint(21) unsigned | NO   |     | 0       |       |
| ALLOCATED_SIZE | bigint(21) unsigned | NO   |     | 0       |       |
+----------------+---------------------+------+-----+---------+-------+

From MariaDB 10.4:

SELECT * FROM information_schema.INNODB_SYS_TABLESPACES LIMIT 2\G
*************************** 1. row ***************************
         SPACE: 2
          NAME: mysql/innodb_table_stats
          FLAG: 33
   FILE_FORMAT: Barracuda
    ROW_FORMAT: Dynamic
     PAGE_SIZE: 16384
 ZIP_PAGE_SIZE: 0
    SPACE_TYPE: Single
 FS_BLOCK_SIZE: 4096
     FILE_SIZE: 98304
ALLOCATED_SIZE: 98304
*************************** 2. row ***************************
         SPACE: 3
          NAME: mysql/innodb_index_stats
          FLAG: 33
   FILE_FORMAT: Barracuda
    ROW_FORMAT: Dynamic
     PAGE_SIZE: 16384
 ZIP_PAGE_SIZE: 0
    SPACE_TYPE: Single
 FS_BLOCK_SIZE: 4096
     FILE_SIZE: 98304
ALLOCATED_SIZE: 98304

1.1.2.9.1.1.1.30 Information Schema INNODB_SYS_TABLESTATS Table

The Information Schema INNODB_SYS_TABLESTATS table contains InnoDB status information. It can be used for developing new performance-related extensions, or high-level performance monitoring.

The PROCESS privilege is required to view the table.

Note that the MySQL InnoDB and Percona XtraDB versions of the tables differ (see XtraDB and InnoDB).

It contains the following columns:

ColumnDescription
TABLE_IDTable ID, matching the INNODB_SYS_TABLES.TABLE_ID value.
SCHEMADatabase name (XtraDB only).
NAMETable name, matching the INNODB_SYS_TABLES.NAME value.
STATS_INITIALIZEDInitialized if statistics have already been collected, otherwise Uninitialized.
NUM_ROWSEstimated number of rows currently in the table. Updated after each statement modifying the data, but uncommited transactions mean it may not be accurate.
CLUST_INDEX_SIZENumber of pages on disk storing the clustered index, holding InnoDB table data in primary key order, or NULL if not statistics yet collected.
OTHER_INDEX_SIZENumber of pages on disk storing secondary indexes for the table, or NULL if not statistics yet collected.
MODIFIED_COUNTERNumber of rows modified by statements modifying data.
AUTOINCAuto_increment value.
REF_COUNTCountdown to zero, when table metadata can be removed from the table cache. (InnoDB only)
MYSQL_HANDLES_OPENED(XtraDB only).

1.1.2.9.1.1.1.31 Information Schema INNODB_SYS_VIRTUAL Table

MariaDB starting with 10.2

The INNODB_SYS_VIRTUAL table was added in MariaDB 10.2.

The Information Schema INNODB_SYS_VIRTUAL table contains information about base columns of virtual columns. The PROCESS privilege is required to view the table.

It contains the following columns:

FieldTypeNullKeyDefaultDescription
TABLE_IDbigint(21) unsignedNO0
POSint(11) unsignedNO0
BASE_POSint(11) unsignedNO0

1.1.2.9.1.1.1.32 Information Schema INNODB_TABLESPACES_ENCRYPTION Table

The Information Schema INNODB_TABLESPACES_ENCRYPTION table contains metadata about encrypted InnoDB tablespaces. When you enable encryption for an InnoDB tablespace, an entry for the tablespace is added to this table. If you later disable encryption for the InnoDB tablespace, then the row still remains in this table, but the ENCRYPTION_SCHEME and CURRENT_KEY_VERSION columns will be set to 0.

Viewing this table requires the PROCESS privilege, although a bug in versions before MariaDB 10.1.46, 10.2.33, 10.3.24, 10.4.14 and 10.5.5 mean the SUPER privilege was required (MDEV-23003).

It has the following columns:

ColumnDescriptionAdded
SPACEInnoDB tablespace ID.
NAMEPath to the InnoDB tablespace file, without the extension.
ENCRYPTION_SCHEMEKey derivation algorithm. Only 1 is currently used to represent an algorithm. If this value is 0, then the tablespace is unencrypted.
KEYSERVER_REQUESTSNumber of times InnoDB has had to request a key from the encryption key management plugin. The three most recent keys are cached internally.
MIN_KEY_VERSIONMinimum key version used to encrypt a page in the tablespace. Different pages may be encrypted with different key versions.
CURRENT_KEY_VERSIONKey version that will be used to encrypt pages. If this value is 0, then the tablespace is unencrypted.
KEY_ROTATION_PAGE_NUMBERPage that a background encryption thread is currently rotating. If key rotation is not enabled, then the value will be NULL.
KEY_ROTATION_MAX_PAGE_NUMBERWhen a background encryption thread starts rotating a tablespace, the field contains its current size. If key rotation is not enabled, then the value will be NULL.
CURRENT_KEY_IDKey ID for the encryption key currently in use.MariaDB 10.1.13
ROTATING_OR_FLUSHINGCurrent key rotation status. If this value is 1, then the background encryption threads are working on the tablespace. See MDEV-11738.MariaDB 10.2.5, MariaDB 10.1.23

When the InnoDB system tablespace is encrypted, it is represented in this table with the special name: innodb_system.

Example

SELECT * FROM information_schema.INNODB_TABLESPACES_ENCRYPTION 
WHERE NAME LIKE 'db_encrypt%';
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
| SPACE | NAME                                         | ENCRYPTION_SCHEME | KEYSERVER_REQUESTS | MIN_KEY_VERSION | CURRENT_KEY_VERSION | KEY_ROTATION_PAGE_NUMBER | KEY_ROTATION_MAX_PAGE_NUMBER |
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
|    18 | db_encrypt/t_encrypted_existing_key          |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    19 | db_encrypt/t_not_encrypted_existing_key      |                 1 |                  0 |               1 |                   1 |                     NULL |                         NULL |
|    20 | db_encrypt/t_not_encrypted_non_existing_key  |                 1 |                  0 |      4294967295 |          4294967295 |                     NULL |                         NULL |
|    21 | db_encrypt/t_default_encryption_existing_key |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    22 | db_encrypt/t_encrypted_default_key           |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    23 | db_encrypt/t_not_encrypted_default_key       |                 1 |                  0 |               1 |                   1 |                     NULL |                         NULL |
|    24 | db_encrypt/t_defaults                        |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
7 rows in set (0.00 sec)

See Also

1.1.2.9.1.1.1.33 Information Schema INNODB_TABLESPACES_SCRUBBING Table

MariaDB 10.1.3 - 10.5.1

InnoDB and XtraDB data scrubbing was introduced in MariaDB 10.1.3. The table was removed in MariaDB 10.5.2 - see MDEV-15528.

The Information Schema INNODB_TABLESPACES_SCRUBBING table contains data scrubbing information.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACEInnoDB table space id number.
NAMEPath to the table space file, without the extension.
COMPRESSEDThe compressed page size, or zero if uncompressed.
LAST_SCRUB_COMPLETEDDate and time when the last scrub was completed, or NULL if never been performed.
CURRENT_SCRUB_STARTEDDate and time when the current scrub started, or NULL if never been performed.
CURRENT_SCRUB_ACTIVE_THREADSNumber of threads currently scrubbing the tablespace.
CURRENT_SCRUB_PAGE_NUMBERPage that the scrubbing thread is currently scrubbing, or NULL if not enabled.
CURRENT_SCRUB_MAX_PAGE_NUMBERWhen a scrubbing starts rotating a table space, the field contains its current size. NULL if not enabled.

Example

SELECT * FROM information_schema.INNODB_TABLESPACES_SCRUBBING LIMIT 1\G
*************************** 1. row ***************************
                        SPACE: 1
                         NAME: mysql/innodb_table_stats
                   COMPRESSED: 0
         LAST_SCRUB_COMPLETED: NULL
        CURRENT_SCRUB_STARTED: NULL
    CURRENT_SCRUB_PAGE_NUMBER: NULL
CURRENT_SCRUB_MAX_PAGE_NUMBER: 0
         ROTATING_OR_FLUSHING: 0
1 rows in set (0.00 sec)

1.1.2.9.1.1.1.34 Information Schema INNODB_TRX Table

The Information Schema INNODB_TRX table stores information about all currently executing InnoDB transactions.

It has the following columns:

ColumnDescription
TRX_IDUnique transaction ID number.
TRX_STATETransaction execution state; one of RUNNING, LOCK WAIT, ROLLING BACK or COMMITTING.
TRX_STARTEDTime that the transaction started.
TRX_REQUESTED_LOCK_IDIf TRX_STATE is LOCK_WAIT, the INNODB_LOCKS.LOCK_ID value of the lock being waited on. NULL if any other state.
TRX_WAIT_STARTEDIf TRX_STATE is LOCK_WAIT, the time the transaction started waiting for the lock, otherwise NULL.
TRX_WEIGHTTransaction weight, based on the number of locked rows and the number of altered rows. To resolve deadlocks, lower weighted transactions are rolled back first. Transactions that have affected non-transactional tables are always treated as having a heavier weight.
TRX_MYSQL_THREAD_IDThread ID from the PROCESSLIST table (note that the locking and transaction information schema tables use a different snapshot from the processlist, so records may appear in one but not the other).
TRX_QUERYSQL that the transaction is currently running.
TRX_OPERATION_STATETransaction's current state, or NULL.
TRX_TABLES_IN_USENumber of InnoDB tables currently being used for processing the current SQL statement.
TRX_TABLES_LOCKEDNumber of InnoDB tables that that have row locks held by the current SQL statement.
TRX_LOCK_STRUCTSNumber of locks reserved by the transaction.
TRX_LOCK_MEMORY_BYTESTotal size in bytes of the memory used to hold the lock structures for the current transaction in memory.
TRX_ROWS_LOCKEDNumber of rows the current transaction has locked. locked by this transaction. An approximation, and may include rows not visible to the current transaction that are delete-marked but physically present.
TRX_ROWS_MODIFIEDNumber of rows added or changed in the current transaction.
TRX_CONCURRENCY_TICKETSIndicates how much work the current transaction can do before being swapped out, see the innodb_concurrency_tickets system variable.
TRX_ISOLATION_LEVELIsolation level of the current transaction.
TRX_UNIQUE_CHECKSWhether unique checks are on or off for the current transaction. Bulk data are a case where unique checks would be off.
TRX_FOREIGN_KEY_CHECKSWhether foreign key checks are on or off for the current transaction. Bulk data are a case where foreign keys checks would be off.
TRX_LAST_FOREIGN_KEY_ERRORError message for the most recent foreign key error, or NULL if none.
TRX_ADAPTIVE_HASH_LATCHEDWhether the adaptive hash index is locked by the current transaction or not. One transaction at a time can change the adaptive hash index.
TRX_ADAPTIVE_HASH_TIMEOUTWhether the adaptive hash index search latch shoild be relinquished immediately or reserved across all MariaDB calls. 0 if there is no contention on the adaptive hash index, in which case the latch is reserved until completion, otherwise counts down to zero and the latch is released after each row lookup.
TRX_IS_READ_ONLY1 if a read-only transaction, otherwise 0.
TRX_AUTOCOMMIT_NON_LOCKING1 if the transaction only contains this one statement, that is, a SELECT statement not using FOR UPDATE or LOCK IN SHARED MODE, and with autocommit on. If this and TRX_IS_READ_ONLY are both 1, the transaction can be optimized by the storrage engine to reduce some overheads

The table is often used in conjunction with the INNODB_LOCKS and INNODB_LOCK_WAITS tables to diagnose problematic locks and transactions.

XA transactions are not stored in this table. To see them, XA RECOVER can be used.

Example

-- session 1
START TRANSACTION;
UPDATE t SET id = 15 WHERE id = 10;

-- session 2
DELETE FROM t WHERE id = 10;

-- session 1
USE information_schema;
SELECT l.*, t.*
    FROM information_schema.INNODB_LOCKS l
    JOIN information_schema.INNODB_TRX t
        ON l.lock_trx_id = t.trx_id
    WHERE trx_state = 'LOCK WAIT' \G
*************************** 1. row ***************************
                   lock_id: 840:40:3:2
               lock_trx_id: 840
                 lock_mode: X
                 lock_type: RECORD
                lock_table: `test`.`t`
                lock_index: PRIMARY
                lock_space: 40
                 lock_page: 3
                  lock_rec: 2
                 lock_data: 10
                    trx_id: 840
                 trx_state: LOCK WAIT
               trx_started: 2019-12-23 18:43:46
     trx_requested_lock_id: 840:40:3:2
          trx_wait_started: 2019-12-23 18:43:46
                trx_weight: 2
       trx_mysql_thread_id: 46
                 trx_query: DELETE FROM t WHERE id = 10
       trx_operation_state: starting index read
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 2
     trx_lock_memory_bytes: 1136
           trx_rows_locked: 1
         trx_rows_modified: 0
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
          trx_is_read_only: 0
trx_autocommit_non_locking: 0

1.1.2.9.1.1.1.35 Information Schema TEMP_TABLES_INFO Table

MariaDB 10.2.2 - 10.2.3

The TEMP_TABLES_INFO table was introduced in MariaDB 10.2.2 and was removed in MariaDB 10.2.4. See MDEV-12459 progress on an alternative.

The Information Schema TEMP_TABLES_INFO table contains information about active InnoDB temporary tables. All user and system-created temporary tables are reported when querying this table, with the exception of optimized internal temporary tables. The data is stored in memory.

Previously, InnoDB temp table metadata was rather stored in InnoDB system tables.

It has the following columns:

ColumnDescription
TABLE_IDTable ID.
NAMETable name.
N_COLSNumber of columns in the temporary table, including three hidden columns that InnoDB creates (DB_ROW_ID, DB_TRX_ID, and DB_ROLL_PTR).
SPACENumerical identifier for the tablespace identifier holding the temporary table. Compressed temporary tables are stored by default in separate per-table tablespaces in the temporary file directory. For non-compressed tables, the shared temporary table is named ibtmp1, found in the data directory. Always a non-zero value, and regenerated on server restart.
PER_TABLE_TABLESPACEIf TRUE, the temporary table resides in a separate per-table tablespace. If FALSE, it resides in the shared temporary tablespace.
IS_COMPRESSEDTRUE if the table is compressed.

The PROCESS privilege is required to view the table.

Examples

CREATE TEMPORARY TABLE t (i INT) ENGINE=INNODB;

SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO;
+----------+--------------+--------+-------+----------------------+---------------+
| TABLE_ID | NAME         | N_COLS | SPACE | PER_TABLE_TABLESPACE | IS_COMPRESSED |
+----------+--------------+--------+-------+----------------------+---------------+
|       39 | #sql1c93_3_1 |      4 |    64 | FALSE                | FALSE         |
+----------+--------------+--------+-------+----------------------+---------------+

Adding a compressed table:

SET GLOBAL innodb_file_format="Barracuda";

CREATE TEMPORARY TABLE t2 (i INT) ROW_FORMAT=COMPRESSED ENGINE=INNODB;

SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO;
+----------+--------------+--------+-------+----------------------+---------------+
| TABLE_ID | NAME         | N_COLS | SPACE | PER_TABLE_TABLESPACE | IS_COMPRESSED |
+----------+--------------+--------+-------+----------------------+---------------+
|       40 | #sql1c93_3_3 |      4 |    65 | TRUE                 | TRUE          |
|       39 | #sql1c93_3_1 |      4 |    64 | FALSE                | FALSE         |
+----------+--------------+--------+-------+----------------------+---------------+

1.1.2.9.1.1.2 Information Schema MyRocks Tables

1.1.2.9.1.1.2. Information Schema ROCKSDB_CFSTATS Table

The Information Schema ROCKSDB_CFSTATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAME
STAT_TYPE
VALUE

1.1.2.9.1.1.2.1 Information Schema ROCKSDB_CF_OPTIONS Table

The Information Schema ROCKSDB_CF_OPTIONS table is included as part of the MyRocks storage engine, and contains infomation about MyRocks column families.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAMEColumn family name.
OPTION_TYPE
VALUE

1.1.2.9.1.1.2.2 Information Schema ROCKSDB_COMPACTION_STATS Table

The Information Schema ROCKSDB_COMPACTION_STATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAME
LEVEL
TYPE
VALUE

1.1.2.9.1.1.2.3 Information Schema ROCKSDB_DBSTATS Table

The Information Schema ROCKSDB_DBSTATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
STAT_TYPE
VALUE

1.1.2.9.1.1.2.4 Information Schema ROCKSDB_DDL Table

The Information Schema ROCKSDB_DDL table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TABLE_SCHEMA
TABLE_NAME
PARTITION_NAME
INDEX_NAME
COLUMN_FAMILY
INDEX_NUMBER
INDEX_TYPE
KV_FORMAT_VERSION
TTL_DURATION
INDEX_FLAGS
CF
AUTO_INCREMENT

1.1.2.9.1.1.2.5 Information Schema ROCKSDB_DEADLOCK Table

The Information Schema ROCKSDB_DEADLOCK table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
DEADLOCK_ID
TIMESTAMP
TRANSACTION_ID
CF_NAME
WAITING_KEY
LOCK_TYPE
INDEX_NAME
TABLE_NAME
ROLLED_BACK

1.1.2.9.1.1.2.6 Information Schema ROCKSDB_GLOBAL_INFO Table

The Information Schema ROCKSDB_GLOBAL_INFO table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TYPE
NAME
VALUE

1.1.2.9.1.1.2.7 Information Schema ROCKSDB_INDEX_FILE_MAP Table

The Information Schema ROCKSDB_INDEX_FILE_MAP table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
COLUMN_FAMILY
INDEX_NUMBER
SST_NAME
NUM_ROWS
DATA_SIZE
ENTRY_DELETES
ENTRY_SINGLEDELETES
ENTRY_MERGES
ENTRY_OTHERS
DISTINCT_KEYS_PREFIX

1.1.2.9.1.1.2.8 Information Schema ROCKSDB_LOCKS Table

The Information Schema ROCKSDB_LOCKS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
COLUMN_FAMILY_ID
TRANSACTION_ID
KEY
MODE

1.1.2.9.1.1.2.9 Information Schema ROCKSDB_PERF_CONTEXT Table

The Information Schema ROCKSDB_PERF_CONTEXT table is included as part of the MyRocks storage engine and includes per-table/partition counters .

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TABLE_SCHEMA
TABLE_NAME
PARTITION_NAME
STAT_TYPE
VALUE

Note: for multi-table queries, all counter increments are "billed" to the first table in the query: https://github.com/facebook/mysql-5.6/issues/1018

1.1.2.9.1.1.2.10 Information Schema ROCKSDB_PERF_CONTEXT_GLOBAL Table

The Information Schema ROCKSDB_PERF_CONTEXT_GLOBAL table is included as part of the MyRocks storage engine and includes global counter information.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
STAT_TYPE
VALUE

1.1.2.9.1.1.2.11 Information Schema ROCKSDB_SST_PROPS Table

The Information Schema ROCKSDB_SST_PROPS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
SST_NAME
COLUMN_FAMILY
DATA_BLOCKS
ENTRIES
RAW_KEY_SIZE
RAW_VALUE_SIZE
DATA_BLOCK_SIZE
INDEX_BLOCK_SIZE
INDEX_PARTITIONS
TOP_LEVEL_INDEX_SIZE
FILTER_BLOCK_SIZE
COMPRESSION_ALGO
CREATION_TIME

1.1.2.9.1.1.2.12 Information Schema ROCKSDB_TRX Table

The Information Schema ROCKSDB_TRX table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TRANSACTION_ID
STATE
NAME
WRITE_COUNT
LOCK_COUNT
TIMEOUT_SEC
WAITING_KEY
WAITING_COLUMN_FAMILY_ID
IS_REPLICATION
SKIP_TRX_API
READ_ONLY
HAS_DEADLOCK_DETECTION
NUM_ONGOING_BULKLOAD
THREAD_ID
QUERY

1.1.2.9.1.1.3 ColumnStore Information Schema Tables

MariaDB ColumnStore has four Information Schema tables that expose information about the table and column storage. These tables were added in version 1.0.5 of ColumnStore and were heavily modified for 1.0.6.

COLUMNSTORE_TABLES

The first table is the INFORMATION_SCHEMA.COLUMNSTORE_TABLES. This contains information about the tables inside ColumnStore. The table layout is as follows:

ColumnDescription
TABLE_SCHEMAThe database schema for the table
TABLE_NAMEThe table name
OBJECT_IDThe ColumnStore object ID for the table
CREATION_DATEThe date the table was created
COLUMN_COUNTThe number of columns in the table
AUTOINCREMENTThe start autoincrement value for the table set during CREATE TABLE

Note: Tables created with ColumnStore 1.0.4 or lower will have the year field of the creation data set incorrectly by 1900 years.

COLUMNSTORE_COLUMNS

The INFORMATION_SCHEMA.COLUMNSTORE_COLUMNS table contains information about every single column inside ColumnStore. The table layout is as follows:

ColumnDescription
TABLE_SCHEMAThe database schema for the table
TABLE_NAMEThe table name for the column
COLUMN_NAMEThe column name
OBJECT_IDThe object ID for the column
DICTIONARY_OBJECT_IDThe dictionary object ID for the column (NULL if there is no dictionary object
LIST_OBJECT_IDPlaceholder for future information
TREE_OBJECT_IDPlaceholder for future information
DATA_TYPEThe data type for the column
COLUMN_LENGTHThe data length for the column
COLUMN_POSITIONThe position of the column in the table, starting at 0
COLUMN_DEFAULTThe default value for the column
IS_NULLABLEWhether or not the column can be set to NULL
NUMERIC_PRECISIONThe numeric precision for the column
NUMERIC_SCALEThe numeric scale for the column
IS_AUTOINCREMENTSet to 1 if the column is an autoincrement column
COMPRESSION_TYPEThe type of compression (either "None" or "Snappy")

COLUMNSTORE_EXTENTS

This table displays the extent map in a user consumable form. An extent is a collection of details about a section of data related to a columnstore column. A majority of columns in ColumnStore will have multiple extents and the columns table above can be joined to this one to filter results by table or column. The table layout is as follows:

ColumnDescription
OBJECT_IDThe object ID for the extent
OBJECT_TYPEWhether this is a "Column" or "Dictionary" extent
LOGICAL_BLOCK_STARTColumnStore's internal start LBID for this extent
LOGICAL_BLOCK_ENDColumnStore's internal end LBID for this extent
MIN_VALUEThis minimum value stored in this extent
MAX_VALUEThe maximum value stored in this extent
WIDTHThe data width for the extent
DBROOTThe DBRoot number for the extent
PARTITION_IDThe parition ID for the extent
SEGMENT_IDThe segment ID for the extent
BLOCK_OFFSETThe block offset for the data file, each data file can contain multiple extents for a column
MAX_BLOCKSThe maximum number of blocks for the extent
HIGH_WATER_MARKThe last block committed to the extent (starting at 0)
STATEThe state of the extent (see below)
STATUSThe availability status for the column which is either "Available", "Unavailable" or "Out of service"
DATA_SIZEThe uncompressed data size for the extent calculated as (HWM + 1) * BLOCK_SIZE

Notes:

  1. The state is "Valid" for a normal state, "Invalid" if a cpimport has completed but the table has not yet been accessed (min/max values will be invalid) or "Updating" if there is a DML statement writing to the column
  2. In ColumnStore the block size is 8192 bytes
  3. By default ColumnStore will write create an extent file of 256*1024*WIDTH bytes for the first partition, if this is too small then for uncompressed data it will create a file of the maximum size for the extent (MAX_BLOCKS * BLOCK_SIZE). Snappy always compression adds a header block.
  4. Object IDs of less than 3000 are for internal tables and will not appear in any of the information schema tables
  5. Prior to 1.0.12 / 1.1.2 DATA_SIZE was incorrectly calculated
  6. HWM is set to zero for the lower segments when there are multiple segments in an extent file, these can be observed when BLOCK_OFFSET > 0
  7. When HWM is 0 the DATA_SIZE will show 0 instead of 8192 to avoid confusion when there is multiple segments in an extent file

COLUMNSTORE_FILES

The columnstore_files table provides information about each file associated with extensions. Each extension can reuse a file at different block offsets so this is not a 1:1 relationship to the columnstore_extents table.

ColumnDescription
OBJECT_IDThe object ID for the extent
SEGMENT_IDThe segment ID for the extent
PARTITION_IDThe partition ID for the extent
FILENAMEThe full path and filename for the extent file, multiple extents for the same column can point to this file with different BLOCK_OFFSETs
FILE_SIZEThe disk file size for the extent
COMPRESSED_DATA_SIZEThe amount of the compressed file used, NULL if this is an uncompressed file

Stored Procedures

A few stored procedures were added in 1.0.6 to provide summaries based on the information schema tables. These can be accessed from the COLUMNSTORE_INFO schema.

total_usage()

The total_usage() procedure gives a total disk usage summary for all the columns in ColumnStore with the exception of the columns used for internal maintenance. It is executed using the following query:

> call columnstore_info.total_usage();

table_usage()

The table_usage() procedure gives a the total data disk usage, dictionary disk usage and grand total disk usage per-table. It can be called in several ways, the first gives a total for each table:

> call columnstore_info.table_usage(NULL, NULL);

Or for a specific table, my_table in my_schema in this example:

> call columnstore_info.table_usage('my_schema', 'my_table');

You can also request all tables for a specified schema:

> call columnstore_info.table_usage('my_schema', NULL);

Note: The quotes around the table name are required, an error will occur without them.

compression_ratio()

The compression_ratio() procedure calculates the average compression ratio across all the compressed extents in ColumnStore. It is called using:

> call columnstore_info.compression_ratio();

Note: The compression ratio is incorrectly calculated before versions 1.0.12 / 1.1.2

1.1.2.9.1.1.4 Information Schema ALL_PLUGINS Table

Description

The Information Schema ALL_PLUGINS table contains information about server plugins, whether installed or not.

It contains the following columns:

ColumnDescription
PLUGIN_NAMEName of the plugin.
PLUGIN_VERSIONVersion from the plugin's general type descriptor.
PLUGIN_STATUSPlugin status, one of ACTIVE, INACTIVE, DISABLED, DELETED or NOT INSTALLED.
PLUGIN_TYPEPlugin type; STORAGE ENGINE, INFORMATION_SCHEMA, AUTHENTICATION, REPLICATION, DAEMON or AUDIT.
PLUGIN_TYPE_VERSIONVersion from the plugin's type-specific descriptor.
PLUGIN_LIBRARYPlugin's shared object file name, located in the directory specified by the plugin_dir system variable, and used by the INSTALL PLUGIN and UNINSTALL PLUGIN statements. NULL if the plugin is complied in and cannot be uninstalled.
PLUGIN_LIBRARY_VERSIONVersion from the plugin's API interface.
PLUGIN_AUTHORAuthor of the plugin.
PLUGIN_DESCRIPTIONDescription.
PLUGIN_LICENSEPlugin's licence.
LOAD_OPTIONHow the plugin was loaded; one of OFF, ON, FORCE or FORCE_PLUS_PERMANENT. See Installing Plugins.
PLUGIN_MATURITYPlugin's maturity level; one of Unknown, Experimental, Alpha, Beta,'Gamma, and Stable.
PLUGIN_AUTH_VERSIONPlugin's version as determined by the plugin author. An example would be '0.99 beta 1'.

It provides a superset of the information shown by the SHOW PLUGINS SONAME statement, as well as the information_schema.PLUGINS table. For specific information about storage engines (a particular type of plugin), see the Information Schema ENGINES table and the SHOW ENGINES statement.

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM information_schema.all_plugins\G
*************************** 1. row ***************************
           PLUGIN_NAME: binlog
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: STORAGE ENGINE
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: MySQL AB
    PLUGIN_DESCRIPTION: This is a pseudo storage engine to represent the binlog in a transaction
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 2. row ***************************
           PLUGIN_NAME: mysql_native_password
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: AUTHENTICATION
   PLUGIN_TYPE_VERSION: 2.1
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: R.J.Silk, Sergei Golubchik
    PLUGIN_DESCRIPTION: Native MySQL authentication
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 3. row ***************************
           PLUGIN_NAME: mysql_old_password
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: AUTHENTICATION
   PLUGIN_TYPE_VERSION: 2.1
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: R.J.Silk, Sergei Golubchik
    PLUGIN_DESCRIPTION: Old MySQL-4.0 authentication
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
...
*************************** 104. row ***************************
           PLUGIN_NAME: WSREP_MEMBERSHIP
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: NOT INSTALLED
           PLUGIN_TYPE: INFORMATION SCHEMA
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: wsrep_info.so
PLUGIN_LIBRARY_VERSION: 1.13
         PLUGIN_AUTHOR: Nirbhay Choubey
    PLUGIN_DESCRIPTION: Information about group members
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: OFF
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 105. row ***************************
           PLUGIN_NAME: WSREP_STATUS
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: NOT INSTALLED
           PLUGIN_TYPE: INFORMATION SCHEMA
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: wsrep_info.so
PLUGIN_LIBRARY_VERSION: 1.13
         PLUGIN_AUTHOR: Nirbhay Choubey
    PLUGIN_DESCRIPTION: Group view information
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: OFF
       PLUGIN_MATURITY: Stable

1.1.2.9.1.1.5 Information Schema APPLICABLE_ROLES Table

The Information Schema APPLICABLE_ROLES table shows the role authorizations that the current user may use.

It contains the following columns:

ColumnDescriptionAdded
GRANTEEAccount that the role was granted to.
ROLE_NAMEName of the role.
IS_GRANTABLEWhether the role can be granted or not.
IS_DEFAULTWhether the role is the user's default role or notMariaDB 10.1.3

The current role is in the ENABLED_ROLES Information Schema table.

Example

SELECT * FROM information_schema.APPLICABLE_ROLES;
+----------------+-------------+--------------+------------+
| GRANTEE        | ROLE_NAME   | IS_GRANTABLE | IS_DEFAULT |
+----------------+-------------+--------------+------------+
| root@localhost | journalist  | YES          | NO         |
| root@localhost | staff       | YES          | NO         |
| root@localhost | dd          | YES          | NO         |
| root@localhost | dog         | YES          | NO         |
+----------------+-------------+--------------+------------+

1.1.2.9.1.1.6 Information Schema CHARACTER_SETS Table

The Information Schema CHARACTER_SETS table contains a list of supported character sets, their default collations and maximum lengths.

It contains the following columns:

ColumnDescription
CHARACTER_SET_NAMEName of the character set.
DEFAULT_COLLATE_NAMEDefault collation used.
DESCRIPTIONCharacter set description.
MAXLENMaximum length.

The SHOW CHARACTER SET statement returns the same results (although in a different order), and both can be refined in the same way. For example, the following two statements return the same results:

SHOW CHARACTER SET WHERE Maxlen LIKE '2';

and

SELECT * FROM information_schema.CHARACTER_SETS 
WHERE MAXLEN LIKE '2';

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels, and Supported Character Sets and Collations for a full list of supported characters sets and collations.

Example

SELECT CHARACTER_SET_NAME FROM information_schema.CHARACTER_SETS 
WHERE DEFAULT_COLLATE_NAME LIKE '%chinese%';
+--------------------+
| CHARACTER_SET_NAME |
+--------------------+
| big5               |
| gb2312             |
| gbk                |
+--------------------+

1.1.2.9.1.1.7 Information Schema CHECK_CONSTRAINTS Table

MariaDB starting with 10.2.22

The Information Schema CHECK_CONSTRAINTS Table was introduced in MariaDB 10.3.10 and MariaDB 10.2.22.

The Information Schema CHECK_CONSTRAINTS table stores metadata about the constraints defined for tables in all databases.

It contains the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways contains the string 'def'.
CONSTRAINT_SCHEMADatabase name.
TABLE_NAMETable name.
CONSTRAINT_NAMEConstraint name.
MariaDB starting with 10.5.10
LEVELType of the constraint ('Column' or 'Table').
CHECK_CLAUSEConstraint clause.

Example

A table with a numeric table check constraint and with a default check constraint name:

CREATE TABLE t ( a int, CHECK (a>10));

To see check constraint call check_constraints table from information schema.

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS\G
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: CONSTRAINT_1
        TABLE_NAME: t
      CHECK_CLAUSE: `a` > 10

A new table check constraint called a_upper:

ALTER TABLE t ADD CONSTRAINT a_upper CHECK (a<100);
SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS\G
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: CONSTRAINT_1
        TABLE_NAME: t
      CHECK_CLAUSE: `a` > 10
*************************** 2. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: a_upper
        TABLE_NAME: t
      CHECK_CLAUSE: `a` < 100

A new table tt with a field check constraint called b , as well as a table check constraint called b_upper:

CREATE TABLE tt(b int CHECK(b>0),CONSTRAINT b_upper CHECK(b<50));

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS;
+--------------------+-------------------+-----------------+------------+--------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_NAME | CHECK_CLAUSE |
+--------------------+-------------------+-----------------+------------+--------------+
| def                | test              | b               | tt         | `b` > 0      |
| def                | test              | b_upper         | tt         | `b` < 50     |
| def                | test              | CONSTRAINT_1    | t          | `a` > 10     |
| def                | test              | a_upper         | t          | `a` < 100    |
+--------------------+-------------------+-----------------+------------+--------------+

Note: The name of the field constraint is the same as the field name.

After dropping the default table constraint called CONSTRAINT_1:

ALTER TABLE t DROP CONSTRAINT CONSTRAINT_1;

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS;
+--------------------+-------------------+-----------------+------------+--------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_NAME | CHECK_CLAUSE |
+--------------------+-------------------+-----------------+------------+--------------+
| def                | test              | b               | tt         | `b` > 0      |
| def                | test              | b_upper         | tt         | `b` < 50     |
| def                | test              | a_upper         | t          | `a` < 100    |
+--------------------+-------------------+-----------------+------------+--------------+

Trying to insert invalid arguments into table t and tt generates an error.

INSERT INTO t VALUES (10),(20),(100);
ERROR 4025 (23000): CONSTRAINT `a_upper` failed for `test`.`t`

INSERT INTO tt VALUES (10),(-10),(100);
ERROR 4025 (23000): CONSTRAINT `b` failed for `test`.`tt`

INSERT INTO tt VALUES (10),(20),(100);
ERROR 4025 (23000): CONSTRAINT `b_upper` failed for `test`.`tt`

From MariaDB 10.5.10:

create table majra(check(x>0), x int, y int check(y < 0), z int,
                              constraint z check(z>0), constraint xyz check(x<10 and y<10 and z<10));
Query OK, 0 rows affected (0.036 sec)

show create table majra;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                                                                                                                                   |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| majra | CREATE TABLE `majra` (
  `x` int(11) DEFAULT NULL,
  `y` int(11) DEFAULT NULL CHECK (`y` < 0),
  `z` int(11) DEFAULT NULL,
  CONSTRAINT `CONSTRAINT_1` CHECK (`x` > 0),
  CONSTRAINT `z` CHECK (`z` > 0),
  CONSTRAINT `xyz` CHECK (`x` < 10 and `y` < 10 and `z` < 10)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)


select * from information_schema.check_constraints where table_name='majra';
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | TABLE_NAME | CONSTRAINT_NAME | LEVEL  | CHECK_CLAUSE                       |
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
| def                | test              | majra      | y               | Column | `y` < 0                            |
| def                | test              | majra      | CONSTRAINT_1    | Table  | `x` > 0                            |
| def                | test              | majra      | z               | Table  | `z` > 0                            |
| def                | test              | majra      | xyz             | Table  | `x` < 10 and `y` < 10 and `z` < 10 |
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
4 rows in set (0.001 sec)

1.1.2.9.1.1.8 Information Schema CLIENT_STATISTICS Table

The Information Schema CLIENT_STATISTICS table holds statistics about client connections. This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
CLIENTVARCHAR(64)The IP address or hostname the connection originated from.
TOTAL_CONNECTIONSINT(21)The number of connections created for this client.
CONCURRENT_CONNECTIONSINT(21)The number of concurrent connections for this client.
CONNECTED_TIMEINT(21)The cumulative number of seconds elapsed while there were connections from this client.
BUSY_TIMEDOUBLEThe cumulative number of seconds there was activity on connections from this client.
CPU_TIMEDOUBLEThe cumulative CPU time elapsed while servicing this client's connections. Note that this number may be wrong on SMP system if there was a CPU migration for the thread during the execution of the query.
BYTES_RECEIVEDINT(21)The number of bytes received from this client's connections.
BYTES_SENTINT(21)The number of bytes sent to this client's connections.
BINLOG_BYTES_WRITTENINT(21)The number of bytes written to the binary log from this client's connections.
ROWS_READINT(21)The number of rows read by this client's connections.
ROWS_SENTINT(21)The number of rows sent by this client's connections.
ROWS_DELETEDINT(21)The number of rows deleted by this client's connections.
ROWS_INSERTEDINT(21)The number of rows inserted by this client's connections.
ROWS_UPDATEDINT(21)The number of rows updated by this client's connections.
SELECT_COMMANDSINT(21)The number of SELECT commands executed from this client's connections.
UPDATE_COMMANDSINT(21)The number of UPDATE commands executed from this client's connections.
OTHER_COMMANDSINT(21)The number of other commands executed from this client's connections.
COMMIT_TRANSACTIONSINT(21)The number of COMMIT commands issued by this client's connections.
ROLLBACK_TRANSACTIONSINT(21)The number of ROLLBACK commands issued by this client's connections.
DENIED_CONNECTIONSINT(21)The number of connections denied to this client.
LOST_CONNECTIONSINT(21)The number of this client's connections that were terminated uncleanly.
ACCESS_DENIEDINT(21)The number of times this client's connections issued commands that were denied.
EMPTY_QUERIESINT(21)The number of times this client's connections sent queries that returned no results to the server.
TOTAL_SSL_CONNECTIONSINT(21)The number of TLS connections created for this client. (>= MariaDB 10.1.1)
MAX_STATEMENT_TIME_EXCEEDEDINT(21)The number of times a statement was aborted, because it was executed longer than its MAX_STATEMENT_TIME threshold. (>= MariaDB 10.1.1)

Example

SELECT * FROM information_schema.CLIENT_STATISTICS\G
*************************** 1. row ***************************
                CLIENT: localhost
     TOTAL_CONNECTIONS: 3
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 4883
             BUSY_TIME: 0.009722
              CPU_TIME: 0.0102131
        BYTES_RECEIVED: 841
            BYTES_SENT: 13897
  BINLOG_BYTES_WRITTEN: 0
             ROWS_READ: 0
             ROWS_SENT: 214
          ROWS_DELETED: 0
         ROWS_INSERTED: 207
          ROWS_UPDATED: 0
       SELECT_COMMANDS: 10
       UPDATE_COMMANDS: 0
        OTHER_COMMANDS: 13
   COMMIT_TRANSACTIONS: 0
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 1

1.1.2.9.1.1.9 Information Schema COLLATION_CHARACTER_SET_APPLICABILITY Table

The Information Schema COLLATION_CHARACTER_SET_APPLICABILITY table shows which character sets are associated with which collations.

It contains the following columns:

ColumnDescription
COLLATION_NAMECollation name.
CHARACTER_SET_NAMEName of the associated character set.

COLLATION_CHARACTER_SET_APPLICABILITY is essentially a subset of the COLLATIONS table.

SELECT COLLATION_NAME,CHARACTER_SET_NAME FROM information_schema.COLLATIONS;

and

SELECT * FROM information_schema.COLLATION_CHARACTER_SET_APPLICABILITY;

will return identical results.

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels.

Example

SELECT * FROM information_schema.COLLATION_CHARACTER_SET_APPLICABILITY 
WHERE CHARACTER_SET_NAME='utf32';
+---------------------+--------------------+
| COLLATION_NAME      | CHARACTER_SET_NAME |
+---------------------+--------------------+
| utf32_general_ci    | utf32              |
| utf32_bin           | utf32              |
| utf32_unicode_ci    | utf32              |
| utf32_icelandic_ci  | utf32              |
| utf32_latvian_ci    | utf32              |
| utf32_romanian_ci   | utf32              |
| utf32_slovenian_ci  | utf32              |
| utf32_polish_ci     | utf32              |
| utf32_estonian_ci   | utf32              |
| utf32_spanish_ci    | utf32              |
| utf32_swedish_ci    | utf32              |
| utf32_turkish_ci    | utf32              |
| utf32_czech_ci      | utf32              |
| utf32_danish_ci     | utf32              |
| utf32_lithuanian_ci | utf32              |
| utf32_slovak_ci     | utf32              |
| utf32_spanish2_ci   | utf32              |
| utf32_roman_ci      | utf32              |
| utf32_persian_ci    | utf32              |
| utf32_esperanto_ci  | utf32              |
| utf32_hungarian_ci  | utf32              |
| utf32_sinhala_ci    | utf32              |
| utf32_german2_ci    | utf32              |
| utf32_croatian_ci   | utf32              |
+---------------------+--------------------+

1.1.2.9.1.1.10 Information Schema COLLATIONS Table

The Information Schema COLLATIONS table contains a list of supported collations.

It contains the following columns:

ColumnDescription
COLLATION_NAMEName of the collation.
CHARACTER_SET_NAMEAssociated character set.
IDCollation id.
IS_DEFAULTWhether the collation is the character set's default.
IS_COMPILEDWhether the collation is compiled into the server.
SORTLENSort length, used for determining the memory used to sort strings in this collation.

The SHOW COLLATION statement returns the same results and both can be reduced in a similar way.

For example, in MariaDB Server 10.6, the following two statements return the same results:

SHOW COLLATION WHERE Charset LIKE 'utf8mb3';

and

SELECT * FROM information_schema.COLLATIONS 
WHERE CHARACTER_SET_NAME LIKE 'utf8mb3';

In MariaDB Server 10.5 and before, utf8 should be specified instead of utf8mb3.

NO PAD collations

MariaDB starting with 10.2

NO PAD collations regard trailing spaces as normal characters. You can get a list of all NO PAD collations as follows:

SELECT collation_name FROM information_schema.COLLATIONS
WHERE collation_name LIKE "%nopad%";  
+------------------------------+
| collation_name               |
+------------------------------+
| big5_chinese_nopad_ci        |
| big5_nopad_bin               |
...

Example

SELECT * FROM information_schema.COLLATIONS;
+------------------------------+--------------------+------+------------+-------------+---------+
| COLLATION_NAME               | CHARACTER_SET_NAME | ID   | IS_DEFAULT | IS_COMPILED | SORTLEN |
+------------------------------+--------------------+------+------------+-------------+---------+
| big5_chinese_ci              | big5               |    1 | Yes        | Yes         |       1 |
| big5_bin                     | big5               |   84 |            | Yes         |       1 |
| big5_chinese_nopad_ci        | big5               | 1025 |            | Yes         |       1 |
| big5_nopad_bin               | big5               | 1108 |            | Yes         |       1 |
| dec8_swedish_ci              | dec8               |    3 | Yes        | Yes         |       1 |
| dec8_bin                     | dec8               |   69 |            | Yes         |       1 |
| dec8_swedish_nopad_ci        | dec8               | 1027 |            | Yes         |       1 |
| dec8_nopad_bin               | dec8               | 1093 |            | Yes         |       1 |
| cp850_general_ci             | cp850              |    4 | Yes        | Yes         |       1 |
| cp850_bin                    | cp850              |   80 |            | Yes         |       1 |
...

See Also

1.1.2.9.1.1.11 Information Schema COLUMN_PRIVILEGES Table

The Information Schema COLUMN_PRIVILEGES table contains column privilege information derived from the mysql.columns_priv grant table.

It has the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
COLUMN_NAMEColumn name.
PRIVILEGE_TYPEOne of SELECT, INSERT, UPDATE or REFERENCES.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW FULL COLUMNS and SHOW GRANTS statements. See the GRANT article for more about privileges.

This information is also stored in the columns_priv table, in the mysql system database.

For a description of the privileges that are shown in this table, see column privileges.

Example

In the following example, no column-level privilege has been explicitly assigned:

SELECT * FROM information_schema.COLUMN_PRIVILEGES;
Empty set

1.1.2.9.1.1.12 Information Schema COLUMNS Table

The Information Schema COLUMNS table provides information about columns in each table on the server.

It contains the following columns:

ColumnDescriptionIntroduced
TABLE_CATALOGAlways contains the string 'def'.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
COLUMN_NAMEColumn name.
ORDINAL_POSITIONColumn position in the table. Can be used for ordering.
COLUMN_DEFAULTDefault value for the column. From MariaDB 10.2.7, literals are quoted to distinguish them from expressions. NULL means that the column has no default. In MariaDB 10.2.6 and earlier, no quotes were used for any type of default and NULL can either mean that there is no default, or that the default column value is NULL.
IS_NULLABLEWhether the column can contain NULLs.
DATA_TYPEThe column's data type.
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
COLUMN_TYPEColumn definition, a MySQL and MariaDB extension.
COLUMN_KEYIndex type. PRI for primary key, UNI for unique index, MUL for multiple index. A MySQL and MariaDB extension.
EXTRAAdditional information about a column, for example whether the column is an invisible column, or, from MariaDB 10.3.6, WITHOUT SYSTEM VERSIONING if the table is not a system-versioned table. A MySQL and MariaDB extension.
PRIVILEGESWhich privileges you have for the column. A MySQL and MariaDB extension.
COLUMN_COMMENTColumn comments.
IS_GENERATEDIndicates whether the column value is generated (virtual, or computed). Can be ALWAYS or NEVER.MariaDB 10.2.5
GENERATION_EXPRESSIONThe expression used for computing the column value in a generated (virtual, or computed) column.MariaDB 10.2.5

It provides information similar to, but more complete, than SHOW COLUMNS and mysqlshow.

Examples

SELECT * FROM information_schema.COLUMNS\G
...
*************************** 9. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t2
             COLUMN_NAME: j
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: NULL
             IS_NULLABLE: YES
               DATA_TYPE: longtext
CHARACTER_MAXIMUM_LENGTH: 4294967295
  CHARACTER_OCTET_LENGTH: 4294967295
       NUMERIC_PRECISION: NULL
           NUMERIC_SCALE: NULL
      DATETIME_PRECISION: NULL
      CHARACTER_SET_NAME: utf8mb4
          COLLATION_NAME: utf8mb4_bin
             COLUMN_TYPE: longtext
              COLUMN_KEY: 
                   EXTRA: 
              PRIVILEGES: select,insert,update,references
          COLUMN_COMMENT: 
            IS_GENERATED: NEVER
   GENERATION_EXPRESSION: NULL
...
CREATE TABLE t (
  s1 VARCHAR(20) DEFAULT 'ABC',
  s2 VARCHAR(20) DEFAULT (concat('A','B')),
  s3 VARCHAR(20) DEFAULT ("concat('A','B')"),
  s4 VARCHAR(20),
  s5 VARCHAR(20) DEFAULT NULL,
  s6 VARCHAR(20) NOT NULL,
  s7 VARCHAR(20) DEFAULT 'NULL' NULL,
  s8 VARCHAR(20) DEFAULT 'NULL' NOT NULL
);

SELECT 
  table_name, 
  column_name, 
  ordinal_position, 
  column_default,
  column_default IS NULL
FROM information_schema.COLUMNS
WHERE table_schema=DATABASE()
AND TABLE_NAME='t';

From MariaDB 10.2.7:

+------------+-------------+------------------+-----------------------+------------------------+
| table_name | column_name | ordinal_position | column_default        | column_default IS NULL |
+------------+-------------+------------------+-----------------------+------------------------+
| t          | s1          |                1 | 'ABC'                 |                      0 |
| t          | s2          |                2 | concat('A','B')       |                      0 |
| t          | s3          |                3 | 'concat(''A'',''B'')' |                      0 |
| t          | s4          |                4 | NULL                  |                      0 |
| t          | s5          |                5 | NULL                  |                      0 |
| t          | s6          |                6 | NULL                  |                      1 |
| t          | s7          |                7 | 'NULL'                |                      0 |
| t          | s8          |                8 | 'NULL'                |                      0 |
+------------+-------------+------------------+-----------------------+------------------------+

In the results above, the two single quotes in concat(''A'',''B'') indicate an escaped single quote - see string-literals. Note that while mysql-command-line-client appears to show the same default value for columns s5 and s6, the first is a 4-character string "NULL", while the second is the SQL NULL value.

MariaDB 10.2.6 and before:

+------------+-------------+------------------+-----------------+------------------------+
| table_name | column_name | ordinal_position | column_default  | column_default IS NULL |
+------------+-------------+------------------+-----------------+------------------------+
| t          | s1          |                1 | ABC             |                      0 |
| t          | s2          |                2 | concat('A','B') |                      0 |
| t          | s3          |                3 | concat('A','B') |                      0 |
| t          | s4          |                4 | NULL            |                      1 |
| t          | s5          |                5 | NULL            |                      1 |
| t          | s6          |                6 | NULL            |                      1 |
| t          | s7          |                7 | NULL            |                      0 |
| t          | s8          |                8 | NULL            |                      0 |
+------------+-------------+------------------+-----------------+------------------------+

1.1.2.9.1.1.13 Information Schema DISKS Table

MariaDB 10.1.32

The DISKS table was introduced in MariaDB 10.1.32, MariaDB 10.2.14, and MariaDB 10.3.6 as part of the DISKS plugin.

Description

The DISKS table is created when the DISKS plugin is enabled, and shows metadata about disks on the system.

Before MariaDB 10.4.7, MariaDB 10.3.17, MariaDB 10.2.26 and MariaDB 10.1.41, this plugin did not check user privileges. When it is enabled, any user can query the INFORMATION_SCHEMA.DISKS table and see all the information it provides.

Since MariaDB 10.4.7, MariaDB 10.3.17, MariaDB 10.2.26 and MariaDB 10.1.41, it requires the FILE privilege.

The plugin only works on Linux.

The table contains the following columns:

ColumnDescription
DISKName of the disk itself.
PATHMount point of the disk.
TOTALTotal space in KiB.
USEDUsed amount of space in KiB.
AVAILABLEAmount of space in KiB available to non-root users.

Note that as the amount of space available to root (OS user) may be more that what is available to non-root users, 'available' + 'used' may be less than 'total'.

All paths to which a particular disk has been mounted are reported. The rationale is that someone might want to take different action e.g. depending on which disk is relevant for a particular path. This leads to the same disk being reported multiple times.

Example

SELECT * FROM information_schema.DISKS;

+-----------+-------+----------+---------+-----------+
| Disk      | Path  | Total    | Used    | Available |
+-----------+-------+----------+---------+-----------+
| /dev/vda1 | /     | 26203116 | 2178424 |  24024692 |
| /dev/vda1 | /boot | 26203116 | 2178424 |  24024692 |
| /dev/vda1 | /etc  | 26203116 | 2178424 |  24024692 |
+-----------+-------+----------+---------+-----------+

See Also

1.1.2.9.1.1.14 Information Schema ENABLED_ROLES Table

The Information Schema ENABLED_ROLES table shows the enabled roles for the current session.

It contains the following column:

ColumnDescription
ROLE_NAMEThe enabled role name, or NULL.

This table lists all roles that are currently enabled, one role per row — the current role, roles granted to the current role, roles granted to these roles and so on. If no role is set, the row contains a NULL value.

The roles that the current user can enable are listed in the APPLICABLE_ROLES Information Schema table.

See also CURRENT_ROLE().

Examples

SELECT * FROM information_schema.ENABLED_ROLES;
+-----------+
| ROLE_NAME |
+-----------+
| NULL      |
+-----------+

SET ROLE staff;

SELECT * FROM information_schema.ENABLED_ROLES;
+-----------+
| ROLE_NAME |
+-----------+
| staff     |
+-----------+

1.1.2.9.1.1.15 Information Schema ENGINES Table

The Information Schema ENGINES table displays status information about the server's storage engines.

It contains the following columns:

ColumnDescription
ENGINEName of the storage engine.
SUPPORTWhether the engine is the default, or is supported or not.
COMMENTStorage engine comments.
TRANSACTIONSWhether or not the engine supports transactions.
XAWhether or not the engine supports XA transactions.
SAVEPOINTSWhether or not savepoints are supported.

It provides identical information to the SHOW ENGINES statement. Since storage engines are plugins, different information about them is also shown in the information_schema.PLUGINS table and by the SHOW PLUGINS statement.

The table is not a standard Information Schema table, and is a MySQL and MariaDB extension.

Note that both MySQL's InnoDB and Percona's XtraDB replacement are labeled as InnoDB. However, if XtraDB is in use, it will be specified in the COMMENT field. See XtraDB and InnoDB. The same applies to FederatedX.

Example

SELECT * FROM information_schema.ENGINES\G;
*************************** 1. row ***************************
      ENGINE: InnoDB
     SUPPORT: DEFAULT
     COMMENT: Supports transactions, row-level locking, and foreign keys
TRANSACTIONS: YES
          XA: YES
  SAVEPOINTS: YES
*************************** 2. row ***************************
      ENGINE: CSV
     SUPPORT: YES
     COMMENT: CSV storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 3. row ***************************
      ENGINE: MyISAM
     SUPPORT: YES
     COMMENT: MyISAM storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 4. row ***************************
      ENGINE: BLACKHOLE
     SUPPORT: YES
     COMMENT: /dev/null storage engine (anything you write to it disappears)
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 5. row ***************************
      ENGINE: FEDERATED
     SUPPORT: YES
     COMMENT: FederatedX pluggable storage engine
TRANSACTIONS: YES
          XA: NO
  SAVEPOINTS: YES
*************************** 6. row ***************************
      ENGINE: MRG_MyISAM
     SUPPORT: YES
     COMMENT: Collection of identical MyISAM tables
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 7. row ***************************
      ENGINE: ARCHIVE
     SUPPORT: YES
     COMMENT: Archive storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 8. row ***************************
      ENGINE: MEMORY
     SUPPORT: YES
     COMMENT: Hash based, stored in memory, useful for temporary tables
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 9. row ***************************
      ENGINE: PERFORMANCE_SCHEMA
     SUPPORT: YES
     COMMENT: Performance Schema
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 10. row ***************************
      ENGINE: Aria
     SUPPORT: YES
     COMMENT: Crash-safe tables with MyISAM heritage
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
10 rows in set (0.00 sec)

Check if a given storage engine is available:

SELECT SUPPORT FROM information_schema.ENGINES WHERE ENGINE LIKE 'tokudb';
Empty set

Check which storage engine supports XA transactions:

SELECT ENGINE FROM information_schema.ENGINES WHERE XA = 'YES';
+--------+
| ENGINE |
+--------+
| InnoDB |
+--------+

1.1.2.9.1.1.16 Information Schema EVENTS Table

The Information Schema EVENTS table stores information about Events on the server.

It contains the following columns:

ColumnDescription
EVENT_CATALOGAlways def.
EVENT_SCHEMADatabase where the event was defined.
EVENT_NAMEEvent name.
DEFINEREvent definer.
TIME_ZONETime zone used for the event's scheduling and execution, by default SYSTEM.
EVENT_BODYSQL.
EVENT_DEFINITIONThe SQL defining the event.
EVENT_TYPEEither ONE TIME or RECURRING.
EXECUTE_ATDATETIME when the event is set to execute, or NULL if recurring.
INTERVAL_VALUENumeric interval between event executions for a recurring event, or NULL if not recurring.
INTERVAL_FIELDInterval unit (e.g., HOUR)
SQL_MODEThe SQL_MODE at the time the event was created.
STARTSStart DATETIME for a recurring event, NULL if not defined or not recurring.
ENDSEnd DATETIME for a recurring event, NULL if not defined or not recurring.
STATUSOne of ENABLED, DISABLED or /SLAVESIDE_DISABLED.
ON_COMPLETIONThe ON COMPLETION clause, either PRESERVE or NOT PRESERVE .
CREATEDWhen the event was created.
LAST_ALTEREDWhen the event was last changed.
LAST_EXECUTEDWhen the event was last run.
EVENT_COMMENTThe comment provided in the CREATE EVENT statement, or an empty string if none.
ORIGINATORMariaDB server ID on which the event was created.
CHARACTER_SET_CLIENTcharacter_set_client system variable session value at the time the event was created.
COLLATION_CONNECTIONcollation_connection system variable session value at the time the event was created.
DATABASE_COLLATIONDatabase collation with which the event is linked.

The SHOW EVENTS and SHOW CREATE EVENT statements provide similar information.

1.1.2.9.1.1.17 Information Schema FEEDBACK Table

The Information Schema FEEDBACK table is created when the Feedback Plugin is enabled, and contains the complete contents submitted by the plugin.

It contains two columns:

ColumnDescription
VARIABLE_NAMEName of the item of information being collected.
VARIABLE_VALUEContents of the item of information being collected.

It is possible to disable automatic collection, by setting the feedback_url variable to an empty string, and to submit the contents manually, as follows:

$ mysql -e 'SELECT * FROM information_schema.FEEDBACK' > report.txt

Then you can send it by opening https://mariadb.org/feedback_plugin/post in your browser, and uploading your generated report.txt. Or you can do it from the command line with (for example):

$ curl -F data=@report.txt https://mariadb.org/feedback_plugin/post

Manual uploading allows you to be absolutely sure that we receive only the data shown in the information_schema.FEEDBACK table and that no private or sensitive information is being sent.

Example

SELECT * FROM information_schema.FEEDBACK\G
...
*************************** 906. row ***************************
 VARIABLE_NAME: Uname_sysname
VARIABLE_VALUE: Linux
*************************** 907. row ***************************
 VARIABLE_NAME: Uname_release
VARIABLE_VALUE: 3.13.0-53-generic
*************************** 908. row ***************************
 VARIABLE_NAME: Uname_version
VARIABLE_VALUE: #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015
*************************** 909. row ***************************
 VARIABLE_NAME: Uname_machine
VARIABLE_VALUE: x86_64
*************************** 910. row ***************************
 VARIABLE_NAME: Uname_distribution
VARIABLE_VALUE: lsb: Ubuntu 14.04.2 LTS
*************************** 911. row ***************************
 VARIABLE_NAME: Collation used latin1_german1_ci
VARIABLE_VALUE: 1
*************************** 912. row ***************************
 VARIABLE_NAME: Collation used latin1_swedish_ci
VARIABLE_VALUE: 18
*************************** 913. row ***************************
 VARIABLE_NAME: Collation used utf8_general_ci
VARIABLE_VALUE: 567
*************************** 914. row ***************************
 VARIABLE_NAME: Collation used latin1_bin
VARIABLE_VALUE: 1
*************************** 915. row ***************************
 VARIABLE_NAME: Collation used binary
VARIABLE_VALUE: 16
*************************** 916. row ***************************
 VARIABLE_NAME: Collation used utf8_bin
VARIABLE_VALUE: 4044

1.1.2.9.1.1.18 Information Schema FILES Table

The FILES tables is unused in MariaDB. See MDEV-11426.

1.1.2.9.1.1.19 Information Schema GEOMETRY_COLUMNS Table

Description

The Information Schema GEOMETRY_COLUMNS table provides support for Spatial Reference systems for GIS data.

It contains the following columns:

ColumnTypeNullDescription
F_TABLE_CATALOGVARCHAR(512)NOTogether with F_TABLE_SCHEMA and F_TABLE_NAME, the fully qualified name of the featured table containing the geometry column.
F_TABLE_SCHEMAVARCHAR(64)NOTogether with F_TABLE_CATALOG and F_TABLE_NAME, the fully qualified name of the featured table containing the geometry column.
F_TABLE_NAMEVARCHAR(64)NOTogether with F_TABLE_CATALOG and F_TABLE_SCHEMA, the fully qualified name of the featured table containing the geometry column.
F_GEOMETRY_COLUMNVARCHAR(64)NOName of the column in the featured table that is the geometry golumn.
G_TABLE_CATALOGVARCHAR(512)NO
G_TABLE_SCHEMAVARCHAR(64)NODatabase name of the table implementing the geometry column.
G_TABLE_NAMEVARCHAR(64)NOTable name that is implementing the geometry column.
G_GEOMETRY_COLUMNVARCHAR(64)NO
STORAGE_TYPETINYINT(2)NOBinary geometry implementation. Always 1 in MariaDB.
GEOMETRY_TYPEINT(7)NOInteger reflecting the type of geometry stored in this column (see table below).
COORD_DIMENSIONTINYINT(2)NONumber of dimensions in the spatial reference system. Always 2 in MariaDB.
MAX_PPRTINYINT(2)NOAlways 0 in MariaDB.
SRIDSMALLINT(5)NOID of the Spatial Reference System used for the coordinate geometry in this table. It is a foreign key reference to the SPATIAL_REF_SYS table.

Storage_type

The integers in the storage_type field match the geometry types as follows:

IntegerType
0GEOMETRY
1POINT
3LINESTRING
5POLYGON
7MULTIPOINT
9MULTILINESTRING
11MULTIPOLYGON

Example

CREATE TABLE g1(g GEOMETRY(9,4) REF_SYSTEM_ID=101);

SELECT * FROM information_schema.GEOMETRY_COLUMNS\G
*************************** 1. row ***************************
  F_TABLE_CATALOG: def
   F_TABLE_SCHEMA: test
     F_TABLE_NAME: g1
F_GEOMETRY_COLUMN: 
  G_TABLE_CATALOG: def
   G_TABLE_SCHEMA: test
     G_TABLE_NAME: g1
G_GEOMETRY_COLUMN: g
     STORAGE_TYPE: 1
    GEOMETRY_TYPE: 0
  COORD_DIMENSION: 2
          MAX_PPR: 0
             SRID: 101

See also

1.1.2.9.1.1.20 Information Schema GLOBAL_STATUS and SESSION_STATUS Tables

The Information Schema GLOBAL_STATUS and SESSION_STATUS tables store a record of all status variables and their global and session values respectively. This is the same information as displayed by the SHOW STATUS commands SHOW GLOBAL STATUS and SHOW SESSION STATUS.

They contain the following columns:

ColumnDescription
VARIABLE_NAMEStatus variable name.
VARIABLE_VALUEGlobal or session value.

Example

SELECT * FROM information_schema.GLOBAL_STATUS;
+-----------------------------------------------+--------------------+
| VARIABLE_NAME                                 | VARIABLE_VALUE     |
+-----------------------------------------------+--------------------+
...
| BINLOG_SNAPSHOT_FILE                          | mariadb-bin.000208 |
| BINLOG_SNAPSHOT_POSITION                      | 369                |
...
| THREADS_CONNECTED                             | 1                  |
| THREADS_CREATED                               | 1                  |
| THREADS_RUNNING                               | 1                  |
| UPTIME                                        | 57358              |
| UPTIME_SINCE_FLUSH_STATUS                     | 57358              |
+-----------------------------------------------+--------------------+

1.1.2.9.1.1.21 Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES Tables

The Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES tables stores a record of all system variables and their global and session values respectively. This is the same information as displayed by the SHOW VARIABLES commands SHOW GLOBAL VARIABLES and SHOW SESSION VARIABLES.

It contains the following columns:

ColumnDescription
VARIABLE_NAMESystem variable name.
VARIABLE_VALUEGlobal or session value.

Example

SELECT * FROM information_schema.GLOBAL_VARIABLES ORDER BY VARIABLE_NAME\G
*************************** 1. row *****************************
 VARIABLE_NAME: ARIA_BLOCK_SIZE
VARIABLE_VALUE: 8192
*************************** 2. row *****************************
 VARIABLE_NAME: ARIA_CHECKPOINT_LOG_ACTIVITY
VARIABLE_VALUE: 1048576
*************************** 3. row *****************************
 VARIABLE_NAME: ARIA_CHECKPOINT_INTERVAL
VARIABLE_VALUE: 30
...
*************************** 455. row ***************************
 VARIABLE_NAME: VERSION_COMPILE_MACHINE
VARIABLE_VALUE: x86_64
*************************** 456. row ***************************
 VARIABLE_NAME: VERSION_COMPILE_OS
VARIABLE_VALUE: debian-linux-gnu
*************************** 457. row ***************************
 VARIABLE_NAME: WAIT_TIMEOUT
VARIABLE_VALUE: 600

1.1.2.9.1.1.22 Information Schema INDEX_STATISTICS Table

The Information Schema INDEX_STATISTICS table shows statistics on index usage and makes it possible to do such things as locating unused indexes and generating the commands to remove them.

This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
TABLE_SCHEMAVARCHAR(192)The schema (database) name.
TABLE_NAMEVARCHAR(192)The table name.
INDEX_NAMEVARCHAR(192)The index name (as visible in SHOW CREATE TABLE).
ROWS_READINT(21)The number of rows read from this index.

Example

SELECT * FROM information_schema.INDEX_STATISTICS 
WHERE TABLE_NAME = "author";
+--------------+------------+------------+-----------+
| TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
+--------------+------------+------------+-----------+
| books        | author     | by_name    |        15 |
+--------------+------------+------------+-----------+

1.1.2.9.1.1.23 Information Schema KEY_CACHES Table

The Information Schema KEY_CACHES table shows statistics about the segmented key cache,.

It contains the following columns:

Column NameDescription
KEY_CACHE_NAMEThe name of the key cache
SEGMENTStotal number of segments (set to NULL for regular key caches)
SEGMENT_NUMBERsegment number (set to NULL for any regular key caches and for rows containing aggregation statistics for segmented key caches)
FULL_SIZEmemory for cache buffers/auxiliary structures
BLOCK_SIZEsize of the blocks
USED_BLOCKSnumber of currently used blocks
UNUSED_BLOCKSnumber of currently unused blocks
DIRTY_BLOCKSnumber of currently dirty blocks
READ_REQUESTSnumber of read requests
READSnumber of actual reads from files into buffers
WRITE_REQUESTSnumber of write requests
WRITESnumber of actual writes from buffers into files

Example

SELECT * FROM information_schema.KEY_CACHES \G
********************** 1. row **********************
KEY_CACHE_NAME: default
SEGMENTS: NULL
SEGMENT_NUMBER: NULL
     FULL_SIZE: 134217728
    BLOCK_SIZE: 1024
   USED_BLOCKS: 36
 UNUSED_BLOCKS: 107146
  DIRTY_BLOCKS: 0
 READ_REQUESTS: 40305
         READS: 21
WRITE_REQUESTS: 19239
        WRITES: 358

1.1.2.9.1.1.24 Information Schema KEY_COLUMN_USAGE Table

The Information Schema KEY_COLUMN_USAGE table shows which key columns have constraints.

It contains the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name of the constraint.
CONSTRAINT_NAMEName of the constraint (PRIMARY for the primary key).
TABLE_CATALOGAlways #def.
TABLE_SCHEMADatabase name of the column constraint.
TABLE_NAMETable name of the column constraint.
COLUMN_NAMEColumn name of the constraint.
ORDINAL_POSITIONPosition of the column within the constraint.
POSITION_IN_UNIQUE_CONSTRAINTFor foreign keys, the position in the unique constraint.
REFERENCED_TABLE_SCHEMAFor foreign keys, the referenced database name.
REFERENCED_TABLE_NAMEFor foreign keys, the referenced table name.
REFERENCED_COLUMN_NAMEFor foreign keys, the referenced column name.

Example

SELECT * FROM information_schema.KEY_COLUMN_USAGE LIMIT 1 \G
********************** 1. row **********************
           CONSTRAINT_CATALOG: def
            CONSTRAINT_SCHEMA: my_website
              CONSTRAINT_NAME: PRIMARY
                TABLE_CATALOG: def
                 TABLE_SCHEMA: users
                  COLUMN_NAME: user_id
             ORDINAL_POSITION: 1
POSITION_IN_UNIQUE_CONSTRAINT: NULL
      REFERENCED_TABLE_SCHEMA: NULL
        REFERENCED_TABLE_NAME: NULL
       REFERENCED_COLUMN_NAME: NULL

See Also

1.1.2.9.1.1.25 Information Schema KEYWORDS Table

MariaDB starting with 10.6.3

The KEYWORDS table was added in MariaDB 10.6.3.

Description

The Information Schema KEYWORDS table contains the list of MariaDB keywords.

It contains a single column:

ColumnDescription
WORDKeyword

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM INFORMATION_SCHEMA.KEYWORDS;
+-------------------------------+
| WORD                          |
+-------------------------------+
| &&                            |
| <=                            |
| <>                            |
| !=                            |
| >=                            |
| <<                            |
| >>                            |
| <=>                           |
| ACCESSIBLE                    |
| ACCOUNT                       |
| ACTION                        |
| ADD                           |
| ADMIN                         |
| AFTER                         |
| AGAINST                       |
| AGGREGATE                     |
| ALL                           |
| ALGORITHM                     |
| ALTER                         |
| ALWAYS                        |
| ANALYZE                       |
| AND                           |
| ANY                           |
| AS                            |
| ASC                           |
| ASCII                         |
| ASENSITIVE                    |
| AT                            |
| ATOMIC                        |
| AUTHORS                       |
| AUTO_INCREMENT                |
| AUTOEXTEND_SIZE               |
| AUTO                          |
| AVG                           |
| AVG_ROW_LENGTH                |
| BACKUP                        |
| BEFORE                        |
| BEGIN                         |
| BETWEEN                       |
| BIGINT                        |
| BINARY                        |
| BINLOG                        |
| BIT                           |
| BLOB                          |
| BLOCK                         |
| BODY                          |
| BOOL                          |
| BOOLEAN                       |
| BOTH                          |
| BTREE                         |
| BY                            |
| BYTE                          |
| CACHE                         |
| CALL                          |
| CASCADE                       |
| CASCADED                      |
| CASE                          |
| CATALOG_NAME                  |
| CHAIN                         |
| CHANGE                        |
| CHANGED                       |
| CHAR                          |
| CHARACTER                     |
| CHARSET                       |
| CHECK                         |
| CHECKPOINT                    |
| CHECKSUM                      |
| CIPHER                        |
| CLASS_ORIGIN                  |
| CLIENT                        |
| CLOB                          |
| CLOSE                         |
| COALESCE                      |
| CODE                          |
| COLLATE                       |
| COLLATION                     |
| COLUMN                        |
| COLUMN_NAME                   |
| COLUMNS                       |
| COLUMN_ADD                    |
| COLUMN_CHECK                  |
| COLUMN_CREATE                 |
| COLUMN_DELETE                 |
| COLUMN_GET                    |
| COMMENT                       |
| COMMIT                        |
| COMMITTED                     |
| COMPACT                       |
| COMPLETION                    |
| COMPRESSED                    |
| CONCURRENT                    |
| CONDITION                     |
| CONNECTION                    |
| CONSISTENT                    |
| CONSTRAINT                    |
| CONSTRAINT_CATALOG            |
| CONSTRAINT_NAME               |
| CONSTRAINT_SCHEMA             |
| CONTAINS                      |
| CONTEXT                       |
| CONTINUE                      |
| CONTRIBUTORS                  |
| CONVERT                       |
| CPU                           |
| CREATE                        |
| CROSS                         |
| CUBE                          |
| CURRENT                       |
| CURRENT_DATE                  |
| CURRENT_POS                   |
| CURRENT_ROLE                  |
| CURRENT_TIME                  |
| CURRENT_TIMESTAMP             |
| CURRENT_USER                  |
| CURSOR                        |
| CURSOR_NAME                   |
| CYCLE                         |
| DATA                          |
| DATABASE                      |
| DATABASES                     |
| DATAFILE                      |
| DATE                          |
| DATETIME                      |
| DAY                           |
| DAY_HOUR                      |
| DAY_MICROSECOND               |
| DAY_MINUTE                    |
| DAY_SECOND                    |
| DEALLOCATE                    |
| DEC                           |
| DECIMAL                       |
| DECLARE                       |
| DEFAULT                       |
| DEFINER                       |
| DELAYED                       |
| DELAY_KEY_WRITE               |
| DELETE                        |
| DELETE_DOMAIN_ID              |
| DESC                          |
| DESCRIBE                      |
| DES_KEY_FILE                  |
| DETERMINISTIC                 |
| DIAGNOSTICS                   |
| DIRECTORY                     |
| DISABLE                       |
| DISCARD                       |
| DISK                          |
| DISTINCT                      |
| DISTINCTROW                   |
| DIV                           |
| DO                            |
| DOUBLE                        |
| DO_DOMAIN_IDS                 |
| DROP                          |
| DUAL                          |
| DUMPFILE                      |
| DUPLICATE                     |
| DYNAMIC                       |
| EACH                          |
| ELSE                          |
| ELSEIF                        |
| ELSIF                         |
| EMPTY                         |
| ENABLE                        |
| ENCLOSED                      |
| END                           |
| ENDS                          |
| ENGINE                        |
| ENGINES                       |
| ENUM                          |
| ERROR                         |
| ERRORS                        |
| ESCAPE                        |
| ESCAPED                       |
| EVENT                         |
| EVENTS                        |
| EVERY                         |
| EXAMINED                      |
| EXCEPT                        |
| EXCHANGE                      |
| EXCLUDE                       |
| EXECUTE                       |
| EXCEPTION                     |
| EXISTS                        |
| EXIT                          |
| EXPANSION                     |
| EXPIRE                        |
| EXPORT                        |
| EXPLAIN                       |
| EXTENDED                      |
| EXTENT_SIZE                   |
| FALSE                         |
| FAST                          |
| FAULTS                        |
| FEDERATED                     |
| FETCH                         |
| FIELDS                        |
| FILE                          |
| FIRST                         |
| FIXED                         |
| FLOAT                         |
| FLOAT4                        |
| FLOAT8                        |
| FLUSH                         |
| FOLLOWING                     |
| FOLLOWS                       |
| FOR                           |
| FORCE                         |
| FOREIGN                       |
| FORMAT                        |
| FOUND                         |
| FROM                          |
| FULL                          |
| FULLTEXT                      |
| FUNCTION                      |
| GENERAL                       |
| GENERATED                     |
| GET_FORMAT                    |
| GET                           |
| GLOBAL                        |
| GOTO                          |
| GRANT                         |
| GRANTS                        |
| GROUP                         |
| HANDLER                       |
| HARD                          |
| HASH                          |
| HAVING                        |
| HELP                          |
| HIGH_PRIORITY                 |
| HISTORY                       |
| HOST                          |
| HOSTS                         |
| HOUR                          |
| HOUR_MICROSECOND              |
| HOUR_MINUTE                   |
| HOUR_SECOND                   |
| ID                            |
| IDENTIFIED                    |
| IF                            |
| IGNORE                        |
| IGNORED                       |
| IGNORE_DOMAIN_IDS             |
| IGNORE_SERVER_IDS             |
| IMMEDIATE                     |
| IMPORT                        |
| INTERSECT                     |
| IN                            |
| INCREMENT                     |
| INDEX                         |
| INDEXES                       |
| INFILE                        |
| INITIAL_SIZE                  |
| INNER                         |
| INOUT                         |
| INSENSITIVE                   |
| INSERT                        |
| INSERT_METHOD                 |
| INSTALL                       |
| INT                           |
| INT1                          |
| INT2                          |
| INT3                          |
| INT4                          |
| INT8                          |
| INTEGER                       |
| INTERVAL                      |
| INVISIBLE                     |
| INTO                          |
| IO                            |
| IO_THREAD                     |
| IPC                           |
| IS                            |
| ISOLATION                     |
| ISOPEN                        |
| ISSUER                        |
| ITERATE                       |
| INVOKER                       |
| JOIN                          |
| JSON                          |
| JSON_TABLE                    |
| KEY                           |
| KEYS                          |
| KEY_BLOCK_SIZE                |
| KILL                          |
| LANGUAGE                      |
| LAST                          |
| LAST_VALUE                    |
| LASTVAL                       |
| LEADING                       |
| LEAVE                         |
| LEAVES                        |
| LEFT                          |
| LESS                          |
| LEVEL                         |
| LIKE                          |
| LIMIT                         |
| LINEAR                        |
| LINES                         |
| LIST                          |
| LOAD                          |
| LOCAL                         |
| LOCALTIME                     |
| LOCALTIMESTAMP                |
| LOCK                          |
| LOCKED                        |
| LOCKS                         |
| LOGFILE                       |
| LOGS                          |
| LONG                          |
| LONGBLOB                      |
| LONGTEXT                      |
| LOOP                          |
| LOW_PRIORITY                  |
| MASTER                        |
| MASTER_CONNECT_RETRY          |
| MASTER_DELAY                  |
| MASTER_GTID_POS               |
| MASTER_HOST                   |
| MASTER_LOG_FILE               |
| MASTER_LOG_POS                |
| MASTER_PASSWORD               |
| MASTER_PORT                   |
| MASTER_SERVER_ID              |
| MASTER_SSL                    |
| MASTER_SSL_CA                 |
| MASTER_SSL_CAPATH             |
| MASTER_SSL_CERT               |
| MASTER_SSL_CIPHER             |
| MASTER_SSL_CRL                |
| MASTER_SSL_CRLPATH            |
| MASTER_SSL_KEY                |
| MASTER_SSL_VERIFY_SERVER_CERT |
| MASTER_USER                   |
| MASTER_USE_GTID               |
| MASTER_HEARTBEAT_PERIOD       |
| MATCH                         |
| MAX_CONNECTIONS_PER_HOUR      |
| MAX_QUERIES_PER_HOUR          |
| MAX_ROWS                      |
| MAX_SIZE                      |
| MAX_STATEMENT_TIME            |
| MAX_UPDATES_PER_HOUR          |
| MAX_USER_CONNECTIONS          |
| MAXVALUE                      |
| MEDIUM                        |
| MEDIUMBLOB                    |
| MEDIUMINT                     |
| MEDIUMTEXT                    |
| MEMORY                        |
| MERGE                         |
| MESSAGE_TEXT                  |
| MICROSECOND                   |
| MIDDLEINT                     |
| MIGRATE                       |
| MINUS                         |
| MINUTE                        |
| MINUTE_MICROSECOND            |
| MINUTE_SECOND                 |
| MINVALUE                      |
| MIN_ROWS                      |
| MOD                           |
| MODE                          |
| MODIFIES                      |
| MODIFY                        |
| MONITOR                       |
| MONTH                         |
| MUTEX                         |
| MYSQL                         |
| MYSQL_ERRNO                   |
| NAME                          |
| NAMES                         |
| NATIONAL                      |
| NATURAL                       |
| NCHAR                         |
| NESTED                        |
| NEVER                         |
| NEW                           |
| NEXT                          |
| NEXTVAL                       |
| NO                            |
| NOMAXVALUE                    |
| NOMINVALUE                    |
| NOCACHE                       |
| NOCYCLE                       |
| NO_WAIT                       |
| NOWAIT                        |
| NODEGROUP                     |
| NONE                          |
| NOT                           |
| NOTFOUND                      |
| NO_WRITE_TO_BINLOG            |
| NULL                          |
| NUMBER                        |
| NUMERIC                       |
| NVARCHAR                      |
| OF                            |
| OFFSET                        |
| OLD_PASSWORD                  |
| ON                            |
| ONE                           |
| ONLINE                        |
| ONLY                          |
| OPEN                          |
| OPTIMIZE                      |
| OPTIONS                       |
| OPTION                        |
| OPTIONALLY                    |
| OR                            |
| ORDER                         |
| ORDINALITY                    |
| OTHERS                        |
| OUT                           |
| OUTER                         |
| OUTFILE                       |
| OVER                          |
| OVERLAPS                      |
| OWNER                         |
| PACKAGE                       |
| PACK_KEYS                     |
| PAGE                          |
| PAGE_CHECKSUM                 |
| PARSER                        |
| PARSE_VCOL_EXPR               |
| PATH                          |
| PERIOD                        |
| PARTIAL                       |
| PARTITION                     |
| PARTITIONING                  |
| PARTITIONS                    |
| PASSWORD                      |
| PERSISTENT                    |
| PHASE                         |
| PLUGIN                        |
| PLUGINS                       |
| PORT                          |
| PORTION                       |
| PRECEDES                      |
| PRECEDING                     |
| PRECISION                     |
| PREPARE                       |
| PRESERVE                      |
| PREV                          |
| PREVIOUS                      |
| PRIMARY                       |
| PRIVILEGES                    |
| PROCEDURE                     |
| PROCESS                       |
| PROCESSLIST                   |
| PROFILE                       |
| PROFILES                      |
| PROXY                         |
| PURGE                         |
| QUARTER                       |
| QUERY                         |
| QUICK                         |
| RAISE                         |
| RANGE                         |
| RAW                           |
| READ                          |
| READ_ONLY                     |
| READ_WRITE                    |
| READS                         |
| REAL                          |
| REBUILD                       |
| RECOVER                       |
| RECURSIVE                     |
| REDO_BUFFER_SIZE              |
| REDOFILE                      |
| REDUNDANT                     |
| REFERENCES                    |
| REGEXP                        |
| RELAY                         |
| RELAYLOG                      |
| RELAY_LOG_FILE                |
| RELAY_LOG_POS                 |
| RELAY_THREAD                  |
| RELEASE                       |
| RELOAD                        |
| REMOVE                        |
| RENAME                        |
| REORGANIZE                    |
| REPAIR                        |
| REPEATABLE                    |
| REPLACE                       |
| REPLAY                        |
| REPLICA                       |
| REPLICAS                      |
| REPLICA_POS                   |
| REPLICATION                   |
| REPEAT                        |
| REQUIRE                       |
| RESET                         |
| RESIGNAL                      |
| RESTART                       |
| RESTORE                       |
| RESTRICT                      |
| RESUME                        |
| RETURNED_SQLSTATE             |
| RETURN                        |
| RETURNING                     |
| RETURNS                       |
| REUSE                         |
| REVERSE                       |
| REVOKE                        |
| RIGHT                         |
| RLIKE                         |
| ROLE                          |
| ROLLBACK                      |
| ROLLUP                        |
| ROUTINE                       |
| ROW                           |
| ROWCOUNT                      |
| ROWNUM                        |
| ROWS                          |
| ROWTYPE                       |
| ROW_COUNT                     |
| ROW_FORMAT                    |
| RTREE                         |
| SAVEPOINT                     |
| SCHEDULE                      |
| SCHEMA                        |
| SCHEMA_NAME                   |
| SCHEMAS                       |
| SECOND                        |
| SECOND_MICROSECOND            |
| SECURITY                      |
| SELECT                        |
| SENSITIVE                     |
| SEPARATOR                     |
| SEQUENCE                      |
| SERIAL                        |
| SERIALIZABLE                  |
| SESSION                       |
| SERVER                        |
| SET                           |
| SETVAL                        |
| SHARE                         |
| SHOW                          |
| SHUTDOWN                      |
| SIGNAL                        |
| SIGNED                        |
| SIMPLE                        |
| SKIP                          |
| SLAVE                         |
| SLAVES                        |
| SLAVE_POS                     |
| SLOW                          |
| SNAPSHOT                      |
| SMALLINT                      |
| SOCKET                        |
| SOFT                          |
| SOME                          |
| SONAME                        |
| SOUNDS                        |
| SOURCE                        |
| STAGE                         |
| STORED                        |
| SPATIAL                       |
| SPECIFIC                      |
| REF_SYSTEM_ID                 |
| SQL                           |
| SQLEXCEPTION                  |
| SQLSTATE                      |
| SQLWARNING                    |
| SQL_BIG_RESULT                |
| SQL_BUFFER_RESULT             |
| SQL_CACHE                     |
| SQL_CALC_FOUND_ROWS           |
| SQL_NO_CACHE                  |
| SQL_SMALL_RESULT              |
| SQL_THREAD                    |
| SQL_TSI_SECOND                |
| SQL_TSI_MINUTE                |
| SQL_TSI_HOUR                  |
| SQL_TSI_DAY                   |
| SQL_TSI_WEEK                  |
| SQL_TSI_MONTH                 |
| SQL_TSI_QUARTER               |
| SQL_TSI_YEAR                  |
| SSL                           |
| START                         |
| STARTING                      |
| STARTS                        |
| STATEMENT                     |
| STATS_AUTO_RECALC             |
| STATS_PERSISTENT              |
| STATS_SAMPLE_PAGES            |
| STATUS                        |
| STOP                          |
| STORAGE                       |
| STRAIGHT_JOIN                 |
| STRING                        |
| SUBCLASS_ORIGIN               |
| SUBJECT                       |
| SUBPARTITION                  |
| SUBPARTITIONS                 |
| SUPER                         |
| SUSPEND                       |
| SWAPS                         |
| SWITCHES                      |
| SYSDATE                       |
| SYSTEM                        |
| SYSTEM_TIME                   |
| TABLE                         |
| TABLE_NAME                    |
| TABLES                        |
| TABLESPACE                    |
| TABLE_CHECKSUM                |
| TEMPORARY                     |
| TEMPTABLE                     |
| TERMINATED                    |
| TEXT                          |
| THAN                          |
| THEN                          |
| TIES                          |
| TIME                          |
| TIMESTAMP                     |
| TIMESTAMPADD                  |
| TIMESTAMPDIFF                 |
| TINYBLOB                      |
| TINYINT                       |
| TINYTEXT                      |
| TO                            |
| TRAILING                      |
| TRANSACTION                   |
| TRANSACTIONAL                 |
| THREADS                       |
| TRIGGER                       |
| TRIGGERS                      |
| TRUE                          |
| TRUNCATE                      |
| TYPE                          |
| TYPES                         |
| UNBOUNDED                     |
| UNCOMMITTED                   |
| UNDEFINED                     |
| UNDO_BUFFER_SIZE              |
| UNDOFILE                      |
| UNDO                          |
| UNICODE                       |
| UNION                         |
| UNIQUE                        |
| UNKNOWN                       |
| UNLOCK                        |
| UNINSTALL                     |
| UNSIGNED                      |
| UNTIL                         |
| UPDATE                        |
| UPGRADE                       |
| USAGE                         |
| USE                           |
| USER                          |
| USER_RESOURCES                |
| USE_FRM                       |
| USING                         |
| UTC_DATE                      |
| UTC_TIME                      |
| UTC_TIMESTAMP                 |
| VALUE                         |
| VALUES                        |
| VARBINARY                     |
| VARCHAR                       |
| VARCHARACTER                  |
| VARCHAR2                      |
| VARIABLES                     |
| VARYING                       |
| VIA                           |
| VIEW                          |
| VIRTUAL                       |
| VISIBLE                       |
| VERSIONING                    |
| WAIT                          |
| WARNINGS                      |
| WEEK                          |
| WEIGHT_STRING                 |
| WHEN                          |
| WHERE                         |
| WHILE                         |
| WINDOW                        |
| WITH                          |
| WITHIN                        |
| WITHOUT                       |
| WORK                          |
| WRAPPER                       |
| WRITE                         |
| X509                          |
| XOR                           |
| XA                            |
| XML                           |
| YEAR                          |
| YEAR_MONTH                    |
| ZEROFILL                      |
| ||                            |
+-------------------------------+
694 rows in set (0.000 sec)

See Also

1.1.2.9.1.1.26 Information Schema LOCALES Table

Description

The Information Schema LOCALES table contains a list of all compiled-in locales. It is only available if the LOCALES plugin has been installed.

It contains the following columns:

ColumnDescription
IDRow ID.
NAMELocale name, for example en_GB.
DESCRIPTIONLocale description, for example English - United Kingdom.
MAX_MONTH_NAME_LENGTHNumeric length of the longest month in the locale
MAX_DAY_NAME_LENGTHNumeric length of the longest day name in the locale.
DECIMAL_POINTDecimal point character (some locales use a comma).
THOUSAND_SEPThousand's character separator,
ERROR_MESSAGE_LANGUAGEError message language.

The table is not a standard Information Schema table, and is a MariaDB extension.

The SHOW LOCALES statement returns a subset of the information.

Example

SELECT * FROM information_schema.LOCALES;
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+
| ID  | NAME  | DESCRIPTION                         | MAX_MONTH_NAME_LENGTH | MAX_DAY_NAME_LENGTH | DECIMAL_POINT | THOUSAND_SEP | ERROR_MESSAGE_LANGUAGE |
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+
|   0 | en_US | English - United States             |                     9 |                   9 | .             | ,            | english                |
|   1 | en_GB | English - United Kingdom            |                     9 |                   9 | .             | ,            | english                |
|   2 | ja_JP | Japanese - Japan                    |                     3 |                   3 | .             | ,            | japanese               |
|   3 | sv_SE | Swedish - Sweden                    |                     9 |                   7 | ,             |              | swedish                |
|   4 | de_DE | German - Germany                    |                     9 |                  10 | ,             | .            | german                 |
|   5 | fr_FR | French - France                     |                     9 |                   8 | ,             |              | french                 |
|   6 | ar_AE | Arabic - United Arab Emirates       |                     6 |                   8 | .             | ,            | english                |
|   7 | ar_BH | Arabic - Bahrain                    |                     6 |                   8 | .             | ,            | english                |
|   8 | ar_JO | Arabic - Jordan                     |                    12 |                   8 | .             | ,            | english                |
...
| 106 | no_NO | Norwegian - Norway                  |                     9 |                   7 | ,             | .            | norwegian              |
| 107 | sv_FI | Swedish - Finland                   |                     9 |                   7 | ,             |              | swedish                |
| 108 | zh_HK | Chinese - Hong Kong SAR             |                     3 |                   3 | .             | ,            | english                |
| 109 | el_GR | Greek - Greece                      |                    11 |                   9 | ,             | .            | greek                  |
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+

1.1.2.9.1.1.27 Information Schema METADATA_LOCK_INFO Table

The Information Schema METADATA_LOCK_INFO table is created by the metadata_lock_info plugin. It shows active metadata locks and user locks (the locks acquired with GET_LOCK).

It has the following columns:

ColumnDescription
THREAD_ID
LOCK_MODEOne of MDL_INTENTION_EXCLUSIVE, MDL_SHARED, MDL_SHARED_HIGH_PRIO, MDL_SHARED_READ, MDL_SHARED_READ_ONLY, MDL_SHARED_WRITE, MDL_SHARED_NO_WRITE, MDL_SHARED_NO_READ_WRITE, MDL_SHARED_UPGRADABLE or MDL_EXCLUSIVE.
LOCK_DURATIONOne of MDL_STATEMENT, MDL_TRANSACTION or MDL_EXPLICIT
LOCK_TYPEOne of Global read lock, Schema metadata lock, Table metadata lock, Stored function metadata lock, Stored procedure metadata lock, Trigger metadata lock, Event metadata lock, Commit lock or User lock.
TABLE_SCHEMA
TABLE_NAME

"LOCK_MODE" Descriptions

The LOCK_MODE column can have the following values:

ValueDescription
MDL_INTENTION_EXCLUSIVEAn intention exclusive metadata lock (IX). Used only for scoped locks. Owner of this type of lock can acquire upgradable exclusive locks on individual objects. Compatible with other IX locks, but is incompatible with scoped S and X locks. IX lock is taken in SCHEMA namespace when we intend to modify object metadata. Object may refer table, stored procedure, trigger, view/etc.
MDL_SHAREDA shared metadata lock (S). To be used in cases when we are interested in object metadata only and there is no intention to access object data (e.g. for stored routines or during preparing prepared statements). We also mis-use this type of lock for open HANDLERs, since lock acquired by this statement has to be compatible with lock acquired by LOCK TABLES ... WRITE statement, i.e. SNRW (We can't get by by acquiring S lock at HANDLER ... OPEN time and upgrading it to SR lock for HANDLER ... READ as it doesn't solve problem with need to abort DML statements which wait on table level lock while having open HANDLER in the same connection). To avoid deadlock which may occur when SNRW lock is being upgraded to X lock for table on which there is an active S lock which is owned by thread which waits in its turn for table-level lock owned by thread performing upgrade we have to use thr_abort_locks_for_thread() facility in such situation. This problem does not arise for locks on stored routines as we don't use SNRW locks for them. It also does not arise when S locks are used during PREPARE calls as table-level locks are not acquired in this case. This lock is taken for global read lock, when caching a stored procedure in memory for the duration of the transaction and for tables used by prepared statements.
MDL_SHARED_HIGH_PRIOA high priority shared metadata lock. Used for cases when there is no intention to access object data (i.e. data in the table). "High priority" means that, unlike other shared locks, it is granted ignoring pending requests for exclusive locks. Intended for use in cases when we only need to access metadata and not data, e.g. when filling an INFORMATION_SCHEMA table. Since SH lock is compatible with SNRW lock, the connection that holds SH lock lock should not try to acquire any kind of table-level or row-level lock, as this can lead to a deadlock. Moreover, after acquiring SH lock, the connection should not wait for any other resource, as it might cause starvation for X locks and a potential deadlock during upgrade of SNW or SNRW to X lock (e.g. if the upgrading connection holds the resource that is being waited for).
MDL_SHARED_READA shared metadata lock (SR) for cases when there is an intention to read data from table. A connection holding this kind of lock can read table metadata and read table data (after acquiring appropriate table and row-level locks). This means that one can only acquire TL_READ, TL_READ_NO_INSERT, and similar table-level locks on table if one holds SR MDL lock on it. To be used for tables in SELECTs, subqueries, and LOCK TABLE ... READ statements.
MDL_SHARED_WRITEA shared metadata lock (SW) for cases when there is an intention to modify (and not just read) data in the table. A connection holding SW lock can read table metadata and modify or read table data (after acquiring appropriate table and row-level locks). To be used for tables to be modified by INSERT, UPDATE, DELETE statements, but not LOCK TABLE ... WRITE or DDL). Also taken by SELECT ... FOR UPDATE.
MDL_SHARED_UPGRADABLEAn upgradable shared metadata lock for cases when there is an intention to modify (and not just read) data in the table. Can be upgraded to MDL_SHARED_NO_WRITE and MDL_EXCLUSIVE. A connection holding SU lock can read table metadata and modify or read table data (after acquiring appropriate table and row-level locks). To be used for the first phase of ALTER TABLE.
MDL_SHARED_READ_ONLYA shared metadata lock for cases when we need to read data from table and block all concurrent modifications to it (for both data and metadata). Used by LOCK TABLES READ statement.
MDL_SHARED_NO_WRITEAn upgradable shared metadata lock which blocks all attempts to update table data, allowing reads. A connection holding this kind of lock can read table metadata and read table data. Can be upgraded to X metadata lock. Note, that since this type of lock is not compatible with SNRW or SW lock types, acquiring appropriate engine-level locks for reading (TL_READ* for MyISAM, shared row locks in InnoDB) should be contention-free. To be used for the first phase of ALTER TABLE, when copying data between tables, to allow concurrent SELECTs from the table, but not UPDATEs.
MDL_SHARED_NO_READ_WRITEAn upgradable shared metadata lock which allows other connections to access table metadata, but not data. It blocks all attempts to read or update table data, while allowing INFORMATION_SCHEMA and SHOW queries. A connection holding this kind of lock can read table metadata modify and read table data. Can be upgraded to X metadata lock. To be used for LOCK TABLES WRITE statement. Not compatible with any other lock type except S and SH.
MDL_EXCLUSIVEAn exclusive metadata lock (X). A connection holding this lock can modify both table's metadata and data. No other type of metadata lock can be granted while this lock is held. To be used for CREATE/DROP/RENAME TABLE statements and for execution of certain phases of other DDL statements.

Examples

User lock:

SELECT GET_LOCK('abc',1000);
+----------------------+
| GET_LOCK('abc',1000) |
+----------------------+
|                    1 |
+----------------------+

SELECT * FROM information_schema.METADATA_LOCK_INFO;
+-----------+--------------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE                | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+--------------------------+---------------+-----------+--------------+------------+
|        61 | MDL_SHARED_NO_READ_WRITE | MDL_EXPLICIT  | User lock | abc          |            |
+-----------+--------------------------+---------------+-----------+--------------+------------+

Table metadata lock:

START TRANSACTION;

INSERT INTO t VALUES (1,2);

SELECT * FROM information_schema.METADATA_LOCK_INFO \G
*************************** 1. row ***************************
    THREAD_ID: 4
    LOCK_MODE: MDL_SHARED_WRITE
LOCK_DURATION: MDL_TRANSACTION
    LOCK_TYPE: Table metadata lock
 TABLE_SCHEMA: test
   TABLE_NAME: t
SELECT * FROM information_schema.METADATA_LOCK_INFO;
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+ 
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Global read lock | | |
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Commit lock | | |
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Schema metadata lock | dbname | |
| 31 | MDL_SHARED_NO_READ_WRITE | MDL_EXPLICIT | Table metadata lock | dbname | exotics |
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+

See also

1.1.2.9.1.1.28 Information Schema MROONGA_STATS Table

The Information Schema MROONGA_STATS table only exists if the Mroonga storage engine is installed, and contains information about its activities.

ColumnDescription
VERSIONMroonga version.
rows_writtenNumber of rows written into Mroonga tables.
rows_readNumber of rows read from all Mroonga tables.

This table always contains 1 row.

1.1.2.9.1.1.29 Information Schema OPTIMIZER_TRACE Table

MariaDB starting with 10.4.3

Optimizer Trace was introduced in MariaDB 10.4.3.

Description

The Information Schema OPTIMIZER_TRACE table contains Optimizer Trace information.

It contains the following columns:

ColumnDescription
QUERYDisplays the query that was asked to be traced.
TRACEA JSON document displaying the stats we collected when the query was run.
MISSING_BYTES_BEYOND_MAX_MEM_SIZEFor huge trace, where the trace is truncated due to the optimizer_trace_max_mem_size limit being reached, displays the bytes that are missing in the trace
INSUFFICENT_PRIVILEGESSet to 1 if the user running the trace does not have the privileges to see the trace.

Structure:

SHOW CREATE TABLE INFORMATION_SCHEMA.OPTIMIZER_TRACE \G
*************************** 1. row ***************************
       Table: OPTIMIZER_TRACE
Create Table: CREATE TEMPORARY TABLE `OPTIMIZER_TRACE` (
  `QUERY` longtext NOT NULL DEFAULT '',
  `TRACE` longtext NOT NULL DEFAULT '',
  `MISSING_BYTES_BEYOND_MAX_MEM_SIZE` int(20) NOT NULL DEFAULT 0,
  `INSUFFICIENT_PRIVILEGES` tinyint(1) NOT NULL DEFAULT 0
) ENGINE=Aria DEFAULT CHARSET=utf8 PAGE_CHECKSUM=0

1.1.2.9.1.1.30 Information Schema PARAMETERS Table

The Information Schema PARAMETERS table stores information about stored procedures and stored functions parameters.

It contains the following columns:

ColumnDescription
SPECIFIC_CATALOGAlways def.
SPECIFIC_SCHEMADatabase name containing the stored routine parameter.
SPECIFIC_NAMEStored routine name.
ORDINAL_POSITIONOrdinal position of the parameter, starting at 1. 0 for a function RETURNS clause.
PARAMETER_MODEOne of IN, OUT, INOUT or NULL for RETURNS.
PARAMETER_NAMEName of the parameter, or NULL for RETURNS.
DATA_TYPEThe column's data type.
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
DTD_IDENTIFIERDescription of the data type.
ROUTINE_TYPEPROCEDURE or FUNCTION.

Information from this table is similar to that found in the param_list column in the mysql.proc table, and the output of the SHOW CREATE PROCEDURE and SHOW CREATE FUNCTION statements.

To obtain information about the routine itself, you can query the Information Schema ROUTINES table.

Example

SELECT * FROM information_schema.PARAMETERS
LIMIT 1 \G
********************** 1. row **********************
        SPECIFIC_CATALOG: def
         SPECIFIC_SCHEMA: accounts
           SPECIFIC_NAME: user_counts
        ORDINAL_POSITION: 1
          PARAMETER_MODE: IN
          PARAMETER_NAME: user_order
               DATA_TYPE: varchar
CHARACTER_MAXIMUM_LENGTH: 255
  CHARACTER_OCTET_LENGTH: 765
       NUMERIC_PRECISION: NULL
           NUMERIC_SCALE: NULL
      DATETIME_PRECISION: NULL
      CHARACTER_SET_NAME: utf8
          COLLATION_NAME: utf8_general_ci
          DTD_IDENTIFIER: varchar(255)
            ROUTINE_TYPE: PROCEDURE

1.1.2.9.1.1.31 Information Schema PARTITIONS Table

The Information Schema PARTITIONS contains information about table partitions, with each record corresponding to a single partition or subpartition of a partitioned table. Each non-partitioned table also has a record in the PARTITIONS table, but most of the values are NULL.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name containing the partition.
PARTITION_NAMEPartition name.
SUBPARTITION_NAMESubpartition name, or NULL if not a subpartition.
PARTITION_ORDINAL_POSITIONOrder of the partition starting from 1.
SUBPARTITION_ORDINAL_POSITIONOrder of the subpartition starting from 1.
PARTITION_METHODThe partitioning type; one of RANGE, LIST, HASH, LINEAR HASH, KEY or LINEAR KEY.
SUBPARTITION_METHODSubpartition type; one of HASH, LINEAR HASH, KEY or LINEAR KEY, or NULL if not a subpartition.
PARTITION_EXPRESSIONExpression used to create the partition by the CREATE TABLE or ALTER TABLE statement.
SUBPARTITION_EXPRESSIONExpression used to create the subpartition by the CREATE TABLE or ALTER TABLE statement, or NULL if not a subpartition.
PARTITION_DESCRIPTIONFor a RANGE partition, contains either MAXINTEGER or an integer, as set in the VALUES LESS THAN clause. For a LIST partition, contains a comma-separated list of integers, as set in the VALUES IN. NULL if another type of partition.
TABLE_ROWSNumber of rows in the table (may be an estimate for some storage engines).
AVG_ROW_LENGTHAverage row length, that is DATA_LENGTH divided by TABLE_ROWS
DATA_LENGTHTotal number of bytes stored in all rows of the partition.
MAX_DATA_LENGTHMaximum bytes that could be stored in the partition.
INDEX_LENGTHSize in bytes of the partition index file.
DATA_FREEUnused bytes allocated to the partition.
CREATE_TIMETime the partition was created
UPDATE_TIMETime the partition was last modified.
CHECK_TIMETime the partition was last checked, or NULL for storage engines that don't record this information.
CHECKSUMChecksum value, or NULL if none.
PARTITION_COMMENTPartition comment, truncated to 80 characters, or an empty string if no comment.
NODEGROUPNode group, only used for MySQL Cluster, defaults to 0.
TABLESPACE_NAMEAlways default.

1.1.2.9.1.1.32 Information Schema PLUGINS Table

The Information Schema PLUGINS table contains information about server plugins.

It contains the following columns:

ColumnDescription
PLUGIN_NAMEName of the plugin.
PLUGIN_VERSIONVersion from the plugin's general type descriptor.
PLUGIN_STATUSPlugin status, one of ACTIVE, INACTIVE, DISABLED or DELETED.
PLUGIN_TYPEPlugin type; STORAGE ENGINE, INFORMATION_SCHEMA, AUTHENTICATION, REPLICATION, DAEMON or AUDIT.
PLUGIN_TYPE_VERSIONVersion from the plugin's type-specific descriptor.
PLUGIN_LIBRARYPlugin's shared object file name, located in the directory specified by the plugin_dir system variable, and used by the INSTALL PLUGIN and UNINSTALL PLUGIN statements. NULL if the plugin is complied in and cannot be uninstalled.
PLUGIN_LIBRARY_VERSIONVersion from the plugin's API interface.
PLUGIN_AUTHORAuthor of the plugin.
PLUGIN_DESCRIPTIONDescription.
PLUGIN_LICENSEPlugin's licence.
LOAD_OPTIONHow the plugin was loaded; one of OFF, ON, FORCE or FORCE_PLUS_PERMANENT. See Installing Plugins.
PLUGIN_MATURITYPlugin's maturity level; one of Unknown, Experimental, Alpha, Beta,'Gamma, and Stable.
PLUGIN_AUTH_VERSIONPlugin's version as determined by the plugin author. An example would be '0.99 beta 1'.

It provides a superset of the information shown by the SHOW PLUGINS statement. For specific information about storage engines (a particular type of plugins), see the information_schema.ENGINES table and the SHOW ENGINES statement.

This table provides a subset of the Information Schema information_schema.ALL_PLUGINS table, which contains all available plugins, installed or not.

The table is not a standard Information Schema table, and is a MariaDB extension.

Examples

The easiest way to get basic information on plugins is with SHOW PLUGINS:

SHOW PLUGINS;

+----------------------------+----------+--------------------+-------------+---------+
| Name                       | Status   | Type               | Library     | License |
+----------------------------+----------+--------------------+-------------+---------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| mysql_native_password      | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| mysql_old_password         | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| MRG_MyISAM                 | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MyISAM                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| CSV                        | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MEMORY                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEDERATED                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| PERFORMANCE_SCHEMA         | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| Aria                       | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| InnoDB                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| INNODB_TRX                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_LOCKS               | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_LOCK_WAITS          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMP                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMP_RESET           | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMPMEM              | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMPMEM_RESET        | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_PAGE         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_PAGE_LRU     | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_POOL_STATS   | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_METRICS             | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_DEFAULT_STOPWORD | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INSERTED         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_DELETED          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_BEING_DELETED    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_CONFIG           | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INDEX_CACHE      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INDEX_TABLE      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_TABLES          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_TABLESTATS      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_INDEXES         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_COLUMNS         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FIELDS          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN_COLS    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| SPHINX                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| ARCHIVE                    | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| BLACKHOLE                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEEDBACK                   | DISABLED | INFORMATION SCHEMA | NULL        | GPL     |
| partition                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| pam                        | ACTIVE   | AUTHENTICATION     | auth_pam.so | GPL     |
+----------------------------+----------+--------------------+-------------+---------+
SELECT LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_NAME LIKE 'tokudb';
Empty set

The equivalent SELECT query would be:

SELECT PLUGIN_NAME, PLUGIN_STATUS, 
PLUGIN_TYPE, PLUGIN_LIBRARY, PLUGIN_LICENSE
FROM INFORMATION_SCHEMA.PLUGINS;

Other SELECT queries can be used to see additional information. For example:

SELECT PLUGIN_NAME, PLUGIN_DESCRIPTION, 
PLUGIN_MATURITY, PLUGIN_AUTH_VERSION
FROM INFORMATION_SCHEMA.PLUGINS
WHERE PLUGIN_TYPE='STORAGE ENGINE'
ORDER BY PLUGIN_MATURITY \G

*************************** 1. row ***************************
        PLUGIN_NAME: FEDERATED
 PLUGIN_DESCRIPTION: FederatedX pluggable storage engine
    PLUGIN_MATURITY: Beta
PLUGIN_AUTH_VERSION: 2.1
*************************** 2. row ***************************
        PLUGIN_NAME: Aria
 PLUGIN_DESCRIPTION: Crash-safe tables with MyISAM heritage
    PLUGIN_MATURITY: Gamma
PLUGIN_AUTH_VERSION: 1.5
*************************** 3. row ***************************
        PLUGIN_NAME: PERFORMANCE_SCHEMA
 PLUGIN_DESCRIPTION: Performance Schema
    PLUGIN_MATURITY: Gamma
PLUGIN_AUTH_VERSION: 0.1
*************************** 4. row ***************************
        PLUGIN_NAME: binlog
 PLUGIN_DESCRIPTION: This is a pseudo storage engine to represent the binlog in a transaction
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 5. row ***************************
        PLUGIN_NAME: MEMORY
 PLUGIN_DESCRIPTION: Hash based, stored in memory, useful for temporary tables
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 6. row ***************************
        PLUGIN_NAME: MyISAM
 PLUGIN_DESCRIPTION: MyISAM storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 7. row ***************************
        PLUGIN_NAME: MRG_MyISAM
 PLUGIN_DESCRIPTION: Collection of identical MyISAM tables
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 8. row ***************************
        PLUGIN_NAME: CSV
 PLUGIN_DESCRIPTION: CSV storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 9. row ***************************
        PLUGIN_NAME: InnoDB
 PLUGIN_DESCRIPTION: Supports transactions, row-level locking, and foreign keys
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.2.5
*************************** 10. row ***************************
        PLUGIN_NAME: BLACKHOLE
 PLUGIN_DESCRIPTION: /dev/null storage engine (anything you write to it disappears)
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 11. row ***************************
        PLUGIN_NAME: ARCHIVE
 PLUGIN_DESCRIPTION: Archive storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 12. row ***************************
        PLUGIN_NAME: partition
 PLUGIN_DESCRIPTION: Partition Storage Engine Helper
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0

Check if a given plugin is available:

SELECT LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_NAME LIKE 'tokudb';
Empty set

Show authentication plugins:

SELECT PLUGIN_NAME, LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_TYPE LIKE 'authentication' \G

*************************** 1. row ***************************
PLUGIN_NAME: mysql_native_password
LOAD_OPTION: FORCE
*************************** 2. row ***************************
PLUGIN_NAME: mysql_old_password
LOAD_OPTION: FORCE

See Also

1.1.2.9.1.1.33 Information Schema PROCESSLIST Table

Contents

  1. Example
  2. See Also

The Information Schema PROCESSLIST table contains information about running threads.

Similar information can also be returned with the SHOW [FULL] PROCESSLIST statement, or the mysqladmin processlist command.

It contains the following columns:

ColumnDescriptionAdded
IDConnection identifier.
USERMariaDB User.
HOSTConnecting host.
DBDefault database, or NULL if none.
COMMANDType of command running, corresponding to the Com_ status variables. See Thread Command Values.
TIMESeconds that the thread has spent on the current COMMAND so far.
STATECurrent state of the thread. See Thread States.
INFOStatement the thread is executing, or NULL if none.
TIME_MSTime in milliseconds with microsecond precision that the thread has spent on the current COMMAND so far (see more).MariaDB 5.1
STAGEThe stage the process is currently in.MariaDB 5.3
MAX_STAGEThe maximum number of stages.MariaDB 5.3
PROGRESSThe progress of the process within the current stage (0-100%).MariaDB 5.3
MEMORY_USEDMemory in bytes used by the thread.MariaDB 10.0.1
EXAMINED_ROWSRows examined by the thread. Only updated by UPDATE, DELETE, and similar statements. For SELECT and other statements, the value remains zero.MariaDB 10.0.1
QUERY_IDQuery ID.MariaDB 10.0.5
INFO_BINARYBinary data informationMariaDB 10.1.5
TIDThread ID (MDEV-6756)MariaDB 10.1.8

Note that as a difference to MySQL, in MariaDB the TIME column (and also the TIME_MS column) are not affected by any setting of @TIMESTAMP. This means that it can be reliably used also for threads that change @TIMESTAMP (such as the replication SQL thread). See also MySQL Bug #22047.

As a consequence of this, the TIME column of SHOW FULL PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST can not be used to determine if a slave is lagging behind. For this, use instead the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS.

Note that the PROGRESS field from the information schema, and the PROGRESS field from SHOW PROCESSLIST display different results. SHOW PROCESSLIST shows the total progress, while the information schema shows the progress for the current stage only.. To retrieve a similar "total" Progress value from information_schema.PROCESSLIST as the one from SHOW PROCESSLIST, use

SELECT CASE WHEN Max_Stage < 2 THEN Progress ELSE (Stage-1)/Max_Stage*100+Progress/Max_Stage END 
  AS Progress FROM INFORMATION_SCHEMA.PROCESSLIST;

Example

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST\G
*************************** 1. row ***************************
           ID: 9
         USER: msandbox
         HOST: localhost
           DB: NULL
      COMMAND: Query
         TIME: 0
        STATE: Filling schema table
         INFO: SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
      TIME_MS: 0.351
        STAGE: 0
    MAX_STAGE: 0
     PROGRESS: 0.000
  MEMORY_USED: 85392
EXAMINED_ROWS: 0
     QUERY_ID: 15
  INFO_BINARY: SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
          TID: 11838
*************************** 2. row ***************************
           ID: 5
         USER: system user
         HOST: 
           DB: NULL
      COMMAND: Daemon
         TIME: 0
        STATE: InnoDB shutdown handler
         INFO: NULL
      TIME_MS: 0.000
        STAGE: 0
    MAX_STAGE: 0
     PROGRESS: 0.000
  MEMORY_USED: 24160
EXAMINED_ROWS: 0
     QUERY_ID: 0
  INFO_BINARY: NULL
          TID: 3856
...

See Also

1.1.2.9.1.1.34 Information Schema PROFILING Table

The Information Schema PROFILING table contains information about statement resource usage. Profiling information is only recorded if the profiling session variable is set to 1.

It contains the following columns:

Column NameDescription
QUERY_IDQuery_ID.
SEQSequence number showing the display order for rows with the same QUERY_ID.
STATEProfiling state.
DURATIONTime in seconds that the statement has been in the current state.
CPU_USERUser CPU usage in seconds.
CPU_SYSTEMSystem CPU usage in seconds.
CONTEXT_VOLUNTARYNumber of voluntary context switches.
CONTEXT_INVOLUNTARYNumber of involuntary context switches.
BLOCK_OPS_INNumber of block input operations.
BLOCK_OPS_OUTNumber of block output operations.
MESSAGES_SENTNumber of communications sent.
MESSAGES_RECEIVEDNumber of communications received.
PAGE_FAULTS_MAJORNumber of major page faults.
PAGE_FAULTS_MINORNumber of minor page faults.
SWAPSNumber of swaps.
SOURCE_FUNCTIONFunction in the source code executed by the profiled state.
SOURCE_FILEFile in the source code executed by the profiled state.
SOURCE_LINELine in the source code executed by the profiled state.

It contains similar information to the SHOW PROFILE and SHOW PROFILES statements.

Profiling is enabled per session. When a session ends, its profiling information is lost.

1.1.2.9.1.1.35 Information Schema QUERY_CACHE_INFO Table

Description

The table is not a standard Information Schema table, and is a MariaDB extension.

The QUERY_CACHE_INFO table is created by the QUERY_CACHE_INFO plugin, and allows you to see the contents of the query cache. It creates a table in the information_schema database that shows all queries that are in the cache. You must have the PROCESS privilege (see GRANT) to use this table.

It contains the following columns:

ColumnDescription
STATEMENT_SCHEMADatabase used when query was included
STATEMENT_TEXTQuery text
RESULT_BLOCKS_COUNTNumber of result blocks
RESULT_BLOCKS_SIZESize in bytes of result blocks
RESULT_BLOCKS_SIZE_USEDSize in bytes of used blocks
LIMITAdded MariaDB 10.1.8.
MAX_SORT_LENGTHAdded MariaDB 10.1.8.
GROUP_CONCAT_MAX_LENGTHAdded MariaDB 10.1.8.
CHARACTER_SET_CLIENTAdded MariaDB 10.1.8.
CHARACTER_SET_RESULTAdded MariaDB 10.1.8.
COLLATION Added MariaDB 10.1.8.
TIMEZONEAdded MariaDB 10.1.8.
DEFAULT_WEEK_FORMATAdded MariaDB 10.1.8.
DIV_PRECISION_INCREMENTAdded MariaDB 10.1.8.
SQL_MODEAdded MariaDB 10.1.8.
LC_TIME_NAMESAdded MariaDB 10.1.8.
CLIENT_LONG_FLAGAdded MariaDB 10.1.8.
CLIENT_PROTOCOL_41Added MariaDB 10.1.8.
PROTOCOL_TYPEAdded MariaDB 10.1.8.
MORE_RESULTS_EXISTSAdded MariaDB 10.1.8.
IN_TRANSAdded MariaDB 10.1.8.
AUTOCOMMITAdded MariaDB 10.1.8.
PACKET_NUMBERAdded MariaDB 10.1.8.
HITSIncremented each time the query cache is hit. Added MariaDB 10.3.2.

For example:

SELECT * FROM information_schema.QUERY_CACHE_INFO;
+------------------+-----------------+---------------------+--------------------+-------------------------+
| STATEMENT_SCHEMA | STATEMENT_TEXT  | RESULT_BLOCKS_COUNT | RESULT_BLOCKS_SIZE | RESULT_BLOCKS_SIZE_USED |
+------------------+-----------------+---------------------+--------------------+-------------------------+
...
| test             | SELECT * FROM a |                   1 |                512 |                     143 |
| test             | select * FROM a |                   1 |                512 |                     143 |
...
+------------------+-----------------+---------------------+--------------------+-------------------------

1.1.2.9.1.1.36 Information Schema QUERY_RESPONSE_TIME Table

Description

The Information Schema QUERY_RESPONSE_TIME table contains information about queries that take a long time to execute . It is only available if the QUERY_RESPONSE_TIME plugin has been installed.

It contains the following columns:

ColumnDescription
TIMETime interval
COUNTCount of queries falling into the time interval
TOTALTotal execution time of all queries for this interval

See QUERY_RESPONSE_TIME plugin for a full description.

The table is not a standard Information Schema table, and is a MariaDB extension.

SHOW QUERY_RESPONSE_TIME is available from MariaDB 10.1.1 as an alternative for retrieving the data.

Example

SELECT * FROM information_schema.QUERY_RESPONSE_TIME;
+----------------+-------+----------------+
| TIME           | COUNT | TOTAL          |
+----------------+-------+----------------+
|       0.000001 |     0 |       0.000000 |
|       0.000010 |    17 |       0.000094 |
|       0.000100 |  4301         0.236555 |
|       0.001000 |  1499 |       0.824450 |
|       0.010000 | 14851 |      81.680502 |
|       0.100000 |  8066 |     443.635693 |
|       1.000000 |     0 |       0.000000 |
|      10.000000 |     0 |       0.000000 |
|     100.000000 |     1 |      55.937094 |
|    1000.000000 |     0 |       0.000000 |
|   10000.000000 |     0 |       0.000000 |
|  100000.000000 |     0 |       0.000000 |
| 1000000.000000 |     0 |       0.000000 |
| TOO LONG       |     0 | TOO LONG       |
+----------------+-------+----------------+

1.1.2.9.1.1.37 Information Schema REFERENTIAL_CONSTRAINTS Table

The Information Schema REFERENTIAL_CONSTRAINTS table contains information about foreign keys. The single columns are listed in the KEY_COLUMN_USAGE table.

It has the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name, together with CONSTRAINT_NAME identifies the foreign key.
CONSTRAINT_NAMEForeign key name, together with CONSTRAINT_SCHEMA identifies the foreign key.
UNIQUE_CONSTRAINT_CATALOGAlways def.
UNIQUE_CONSTRAINT_SCHEMADatabase name, together with UNIQUE_CONSTRAINT_NAME and REFERENCED_TABLE_NAME identifies the referenced key.
UNIQUE_CONSTRAINT_NAMEReferenced key name, together with UNIQUE_CONSTRAINT_SCHEMA and REFERENCED_TABLE_NAME identifies the referenced key.
MATCH_OPTIONAlways NONE.
UPDATE_RULEThe Update Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.
DELETE_RULEThe Delete Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.
TABLE_NAMETable name from the TABLE_CONSTRAINTS table.
REFERENCED_TABLE_NAMEReferenced key table name, together with UNIQUE_CONSTRAINT_SCHEMA and UNIQUE_CONSTRAINT_NAME identifies the referenced key.

1.1.2.9.1.1.38 Information Schema ROUTINES Table

The Information Schema ROUTINES table stores information about stored procedures and stored functions.

It contains the following columns:

ColumnDescription
SPECIFIC_NAME
ROUTINE_CATALOGAlways def.
ROUTINE_SCHEMADatabase name associated with the routine.
ROUTINE_NAMEName of the routine.
ROUTINE_TYPEWhether the routine is a PROCEDURE or a FUNCTION.
DATA_TYPEThe return value's data type (for stored functions).
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
DATA_TYPEThe column's data type.
ROUTINE_BODYAlways SQL.
ROUTINE_DEFINITIONDefinition of the routine.
EXTERNAL_NAMEAlways NULL.
EXTERNAL_LANGUAGEAlways SQL.
PARAMETER_STYLEAlways SQL.
IS_DETERMINISTICWhether the routine is deterministic (can produce only one result for a given list of parameters) or not.
SQL_DATA_ACCESSOne of READS SQL DATA, MODIFIES SQL DATA, CONTAINS SQL, or NO SQL.
SQL_PATHAlways NULL.
SECURITY_TYPEINVOKER or DEFINER. Indicates which user's privileges apply to this routine.
CREATEDDate and time the routine was created.
LAST_ALTEREDDate and time the routine was last changed.
SQL_MODEThe SQL_MODE at the time the routine was created.
ROUTINE_COMMENTComment associated with the routine.
DEFINERIf the SECURITY_TYPE is DEFINER, this value indicates which user defined this routine.
CHARACTER_SET_CLIENTThe character set used by the client that created the routine.
COLLATION_CONNECTIONThe collation (and character set) used by the connection that created the routine.
DATABASE_COLLATIONThe default collation (and character set) for the database, at the time the routine was created.

It provides information similar to, but more complete, than the SHOW PROCEDURE STATUS and SHOW FUNCTION STATUS statements.

For information about the parameters accepted by the routine, you can query the information_schema.PARAMETERS table.

See also

1.1.2.9.1.1.39 Information Schema SCHEMA_PRIVILEGES Table

The Information Schema SCHEMA_PRIVILEGES table contains information about database privileges.

It contains the following columns:

ColumnDescription
GRANTEEAccount granted the privilege in the format user_name@host_name.
TABLE_CATALOGAlways def
TABLE_SCHEMADatabase name.
PRIVILEGE_TYPEThe granted privilege.
IS_GRANTABLEWhether the privilege can be granted.

The same information in a different format can be found in the mysql.db table.

1.1.2.9.1.1.40 Information Schema SCHEMATA Table

The Information Schema SCHEMATA table stores information about databases on the server.

It contains the following columns:

ColumnDescription
CATALOG_NAMEAlways def.
SCHEMA_NAMEDatabase name.
DEFAULT_CHARACTER_SET_NAMEDefault character set for the database.
DEFAULT_COLLATION_NAMEDefault collation.
SQL_PATHAlways NULL.
SCHEMA_COMMENTDatabase comment. From MariaDB 10.5.0.

Example

SELECT * FROM INFORMATION_SCHEMA.SCHEMATA\G
*************************** 1. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: information_schema
DEFAULT_CHARACTER_SET_NAME: utf8
    DEFAULT_COLLATION_NAME: utf8_general_ci
                  SQL_PATH: NULL
*************************** 2. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: mysql
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
*************************** 3. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: performance_schema
DEFAULT_CHARACTER_SET_NAME: utf8
    DEFAULT_COLLATION_NAME: utf8_general_ci
                  SQL_PATH: NULL
*************************** 4. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: test
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
...

From MariaDB 10.5.0:

SELECT * FROM INFORMATION_SCHEMA.SCHEMATA\G
...
*************************** 2. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: presentations
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
            SCHEMA_COMMENT: Presentations for conferences
...

See Also

1.1.2.9.1.1.41 Information Schema SPATIAL_REF_SYS Table

MariaDB starting with 10.1.2

The SPATIAL_REF_SYS table was introduced in MariaDB 10.1.2

Description

The Information Schema SPATIAL_REF_SYS table stores information on each spatial reference system used in the database.

It contains the following columns:

ColumnTypeNullDescription
SRIDsmallint(5)NOAn integer value that uniquely identifies each Spatial Reference System within a database.
AUTH_NAMEvarchar(512)NOThe name of the standard or standards body that is being cited for this reference system.
AUTH_SRIDsmallint(5)NOThe numeric ID of the coordinate system in the above authority's catalog.
SRTEXTvarchar(2048)NOThe Well-known Text Representation of the Spatial Reference System.

Note: See MDEV-7540.

See also

1.1.2.9.1.1.42 Information Schema SPIDER_ALLOC_MEM Table

The Information Schema SPIDER_ALLOC_MEM table is installed along with the Spider storage engine. It shows information about Spider's memory usage.

It contains the following columns:

ColumnDescription
ID
FUNC_NAME
FILE_NAME
LINE_NO
TOTAL_ALLOC_MEM
CURRENT_ALLOC_MEM
ALLOC_MEM_COUNT
FREE_MEM_COUNT

1.1.2.9.1.1.43 Information Schema SPIDER_WRAPPER_PROTOCOLS Table

MariaDB starting with 10.5.4

The Information Schema SPIDER_WRAPPER_PROTOCOLS table is installed along with the Spider storage engine from MariaDB 10.5.4.

It contains the following columns:

ColumnTypeDescription
WRAPPER_NAMEvarchar(64)
WRAPPER_VERSIONvarchar(20)
WRAPPER_DESCRIPTIONlongtext
WRAPPER_MATURITYvarchar(12)

1.1.2.9.1.1.44 Information Schema SQL_FUNCTIONS Table

MariaDB starting with 10.6.3

The SQL_FUNCTIONS table was added in MariaDB 10.6.3.

Description

The Information Schema SQL_FUNCTIONS table contains the list of MariaDB functions.

It contains a single column:

ColumnDescription
FUNCTIONFunction name

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM INFORMATION_SCHEMA.SQL_FUNCTIONS;
+---------------------------+
| FUNCTION                  |
+---------------------------+
| ADDDATE                   |
| ADD_MONTHS                |
| BIT_AND                   |
| BIT_OR                    |
| BIT_XOR                   |
| CAST                      |
| COUNT                     |
| CUME_DIST                 |
| CURDATE                   |
| CURTIME                   |
| DATE_ADD                  |
| DATE_SUB                  |
| DATE_FORMAT               |
| DECODE                    |
| DENSE_RANK                |
| EXTRACT                   |
| FIRST_VALUE               |
| GROUP_CONCAT              |
| JSON_ARRAYAGG             |
| JSON_OBJECTAGG            |
| LAG                       |
| LEAD                      |
| MAX                       |
| MEDIAN                    |
| MID                       |
| MIN                       |
| NOW                       |
| NTH_VALUE                 |
| NTILE                     |
| POSITION                  |
| PERCENT_RANK              |
| PERCENTILE_CONT           |
| PERCENTILE_DISC           |
| RANK                      |
| ROW_NUMBER                |
| SESSION_USER              |
| STD                       |
| STDDEV                    |
| STDDEV_POP                |
| STDDEV_SAMP               |
| SUBDATE                   |
| SUBSTR                    |
| SUBSTRING                 |
| SUM                       |
| SYSTEM_USER               |
| TRIM                      |
| TRIM_ORACLE               |
| VARIANCE                  |
| VAR_POP                   |
| VAR_SAMP                  |
| ABS                       |
| ACOS                      |
| ADDTIME                   |
| AES_DECRYPT               |
| AES_ENCRYPT               |
| ASIN                      |
| ATAN                      |
| ATAN2                     |
| BENCHMARK                 |
| BIN                       |
| BINLOG_GTID_POS           |
| BIT_COUNT                 |
| BIT_LENGTH                |
| CEIL                      |
| CEILING                   |
| CHARACTER_LENGTH          |
| CHAR_LENGTH               |
| CHR                       |
| COERCIBILITY              |
| COLUMN_CHECK              |
| COLUMN_EXISTS             |
| COLUMN_LIST               |
| COLUMN_JSON               |
| COMPRESS                  |
| CONCAT                    |
| CONCAT_OPERATOR_ORACLE    |
| CONCAT_WS                 |
| CONNECTION_ID             |
| CONV                      |
| CONVERT_TZ                |
| COS                       |
| COT                       |
| CRC32                     |
| DATEDIFF                  |
| DAYNAME                   |
| DAYOFMONTH                |
| DAYOFWEEK                 |
| DAYOFYEAR                 |
| DEGREES                   |
| DECODE_HISTOGRAM          |
| DECODE_ORACLE             |
| DES_DECRYPT               |
| DES_ENCRYPT               |
| ELT                       |
| ENCODE                    |
| ENCRYPT                   |
| EXP                       |
| EXPORT_SET                |
| EXTRACTVALUE              |
| FIELD                     |
| FIND_IN_SET               |
| FLOOR                     |
| FORMAT                    |
| FOUND_ROWS                |
| FROM_BASE64               |
| FROM_DAYS                 |
| FROM_UNIXTIME             |
| GET_LOCK                  |
| GREATEST                  |
| HEX                       |
| IFNULL                    |
| INSTR                     |
| ISNULL                    |
| IS_FREE_LOCK              |
| IS_USED_LOCK              |
| JSON_ARRAY                |
| JSON_ARRAY_APPEND         |
| JSON_ARRAY_INSERT         |
| JSON_COMPACT              |
| JSON_CONTAINS             |
| JSON_CONTAINS_PATH        |
| JSON_DEPTH                |
| JSON_DETAILED             |
| JSON_EXISTS               |
| JSON_EXTRACT              |
| JSON_INSERT               |
| JSON_KEYS                 |
| JSON_LENGTH               |
| JSON_LOOSE                |
| JSON_MERGE                |
| JSON_MERGE_PATCH          |
| JSON_MERGE_PRESERVE       |
| JSON_QUERY                |
| JSON_QUOTE                |
| JSON_OBJECT               |
| JSON_REMOVE               |
| JSON_REPLACE              |
| JSON_SET                  |
| JSON_SEARCH               |
| JSON_TYPE                 |
| JSON_UNQUOTE              |
| JSON_VALID                |
| JSON_VALUE                |
| LAST_DAY                  |
| LAST_INSERT_ID            |
| LCASE                     |
| LEAST                     |
| LENGTH                    |
| LENGTHB                   |
| LN                        |
| LOAD_FILE                 |
| LOCATE                    |
| LOG                       |
| LOG10                     |
| LOG2                      |
| LOWER                     |
| LPAD                      |
| LPAD_ORACLE               |
| LTRIM                     |
| LTRIM_ORACLE              |
| MAKEDATE                  |
| MAKETIME                  |
| MAKE_SET                  |
| MASTER_GTID_WAIT          |
| MASTER_POS_WAIT           |
| MD5                       |
| MONTHNAME                 |
| NAME_CONST                |
| NVL                       |
| NVL2                      |
| NULLIF                    |
| OCT                       |
| OCTET_LENGTH              |
| ORD                       |
| PERIOD_ADD                |
| PERIOD_DIFF               |
| PI                        |
| POW                       |
| POWER                     |
| QUOTE                     |
| REGEXP_INSTR              |
| REGEXP_REPLACE            |
| REGEXP_SUBSTR             |
| RADIANS                   |
| RAND                      |
| RELEASE_ALL_LOCKS         |
| RELEASE_LOCK              |
| REPLACE_ORACLE            |
| REVERSE                   |
| ROUND                     |
| RPAD                      |
| RPAD_ORACLE               |
| RTRIM                     |
| RTRIM_ORACLE              |
| SEC_TO_TIME               |
| SHA                       |
| SHA1                      |
| SHA2                      |
| SIGN                      |
| SIN                       |
| SLEEP                     |
| SOUNDEX                   |
| SPACE                     |
| SQRT                      |
| STRCMP                    |
| STR_TO_DATE               |
| SUBSTR_ORACLE             |
| SUBSTRING_INDEX           |
| SUBTIME                   |
| SYS_GUID                  |
| TAN                       |
| TIMEDIFF                  |
| TIME_FORMAT               |
| TIME_TO_SEC               |
| TO_BASE64                 |
| TO_CHAR                   |
| TO_DAYS                   |
| TO_SECONDS                |
| UCASE                     |
| UNCOMPRESS                |
| UNCOMPRESSED_LENGTH       |
| UNHEX                     |
| UNIX_TIMESTAMP            |
| UPDATEXML                 |
| UPPER                     |
| UUID                      |
| UUID_SHORT                |
| VERSION                   |
| WEEKDAY                   |
| WEEKOFYEAR                |
| WSREP_LAST_WRITTEN_GTID   |
| WSREP_LAST_SEEN_GTID      |
| WSREP_SYNC_WAIT_UPTO_GTID |
| YEARWEEK                  |
+---------------------------+
234 rows in set (0.001 sec)

See Also

1.1.2.9.1.1.45 Information Schema STATISTICS Table

The Information Schema STATISTICS table provides information about table indexes.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
NON_UNIQUE1 if the index can have duplicates, 0 if not.
INDEX_SCHEMADatabase name.
INDEX_NAMEIndex name. The primary key is always named PRIMARY.
SEQ_IN_INDEXThe column sequence number, starting at 1.
COLUMN_NAMEColumn name.
COLLATIONA for sorted in ascending order, or NULL for unsorted.
CARDINALITYEstimate of the number of unique values stored in the index based on statistics stored as integers. Higher cardinalities usually mean a greater chance of the index being used in a join. Updated by the ANALYZE TABLE statement or myisamchk -a.
SUB_PARTNULL if the whole column is indexed, or the number of indexed characters if partly indexed.
PACKEDNULL if not packed, otherwise how the index is packed.
NULLABLEYES if the column may contain NULLs, empty string if not.
INDEX_TYPEIndex type, one of BTREE, RTREE, HASH or FULLTEXT. See Storage Engine Index Types.
COMMENTIndex comments from the CREATE INDEX statement.
IGNOREDWhether or not an index will be ignored by the optimizer. See Ignored Indexes. From MariaDB 10.6.0.

The SHOW INDEX statement produces similar output.

Example

SELECT * FROM INFORMATION_SCHEMA.STATISTICS\G
...
*************************** 85. row ***************************
TABLE_CATALOG: def
 TABLE_SCHEMA: test
   TABLE_NAME: table1
   NON_UNIQUE: 1
 INDEX_SCHEMA: test
   INDEX_NAME: col2
 SEQ_IN_INDEX: 1
  COLUMN_NAME: col2
    COLLATION: A
  CARDINALITY: 6
     SUB_PART: NULL
       PACKED: NULL
     NULLABLE: 
   INDEX_TYPE: BTREE
      COMMENT: 
INDEX_COMMENT:
...

1.1.2.9.1.1.46 Information Schema SYSTEM_VARIABLES Table

MariaDB starting with 10.1.1

The information_schema.SYSTEM_VARIABLES table was introduced in MariaDB 10.1.1

The Information Schema SYSTEM_VARIABLES table shows current values and various metadata of all system variables.

It contains the following columns:

ColumnDescription
VARIABLE_NAMESystem variable name.
SESSION_VALUESession value of the variable or NULL if the variable only has a global scope.
GLOBAL_VALUEGlobal value of the variable or NULL if the variable only has a session scope.
GLOBAL_VALUE_ORIGINHow the global value was set — a compile-time default, auto-configured by the server, configuration file (or a command line), with the SQL statement.
DEFAULT_VALUECompile-time default value of the variable.
VARIABLE_SCOPEGlobal, session, or session-only.
VARIABLE_TYPEData type of the variable value.
VARIABLE_COMMENTHelp text, usually shown in mysqld --help --verbose.
NUMERIC_MIN_VALUEFor numeric variables — minimal allowed value.
NUMERIC_MAX_VALUEFor numeric variables — maximal allowed value.
NUMERIC_BLOCK_SIZEFor numeric variables — a valid value must be a multiple of the "block size".
ENUM_VALUE_LISTFor ENUM, SET, and FLAGSET variables — the list of recognized values.
READ_ONLYWhether a variable can be set with the SQL statement. Note that many "read only" variables can still be set on the command line.
COMMAND_LINE_ARGUMENTWhether an argument is required when setting the variable on the command line. NULL when a variable can not be set on the command line.
GLOBAL_VALUE_PATHWhich config file the variable got its value from. NULL if not set in any config file. Added in MariaDB 10.5.0.

Example

SELECT * FROM information_schema.SYSTEM_VARIABLES 
  WHERE VARIABLE_NAME='JOIN_BUFFER_SIZE'\G
*************************** 1. row *****************************
        VARIABLE_NAME: JOIN_BUFFER_SIZE
        SESSION_VALUE: 131072
         GLOBAL_VALUE: 131072
  GLOBAL_VALUE_ORIGIN: COMPILE-TIME
        DEFAULT_VALUE: 131072
       VARIABLE_SCOPE: SESSION
        VARIABLE_TYPE: BIGINT UNSIGNED
     VARIABLE_COMMENT: The size of the buffer that is used for joins
    NUMERIC_MIN_VALUE: 128
    NUMERIC_MAX_VALUE: 18446744073709551615
   NUMERIC_BLOCK_SIZE: 128
      ENUM_VALUE_LIST: NULL
            READ_ONLY: NO
COMMAND_LINE_ARGUMENT: REQUIRED

1.1.2.9.1.1.47 Information Schema TABLE_CONSTRAINTS Table

The Information Schema TABLE_CONSTRAINTS table contains information about tables that have constraints.

It has the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name containing the constraint.
CONSTRAINT_NAMEConstraint name.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
CONSTRAINT_TYPEType of constraint; one of UNIQUE, PRIMARY KEY, FOREIGN KEY or CHECK.

The REFERENTIAL_CONSTRAINTS table has more information about foreign keys.

1.1.2.9.1.1.48 Information Schema TABLE_PRIVILEGES Table

The Information Schema TABLE_PRIVILEGES table contains table privilege information derived from the mysql.tables_priv grant table.

It has the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
PRIVILEGE_TYPEOne of SELECT, INSERT, UPDATE, REFERENCES, ALTER, INDEX, DROP or CREATE VIEW.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW GRANTS statement. See the GRANT article for more about privileges.

For a description of the privileges that are shown in this table, see table privileges.

1.1.2.9.1.1.49 Information Schema TABLE_STATISTICS Table

The Information Schema TABLE_STATISTICS table shows statistics on table usage.

This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
TABLE_SCHEMAvarchar(192)The schema (database) name.
TABLE_NAMEvarchar(192)The table name.
ROWS_READint(21)The number of rows read from the table.
ROWS_CHANGEDint(21)The number of rows changed in the table.
ROWS_CHANGED_X_INDEXESint(21)The number of rows changed in the table, multiplied by the number of indexes changed.

Example

SELECT * FROM INFORMATION_SCHEMA.TABLE_STATISTICS WHERE TABLE_NAME='user';
+--------------+------------+-----------+--------------+------------------------+
| TABLE_SCHEMA | TABLE_NAME | ROWS_READ | ROWS_CHANGED | ROWS_CHANGED_X_INDEXES |
+--------------+------------+-----------+--------------+------------------------+
| mysql        | user       |         5 |            2 |                      2 |
+--------------+------------+-----------+--------------+------------------------+

1.1.2.9.1.1.50 Information Schema TABLES Table

The Information Schema table shows information about the various non-TEMPORARY tables (except tables from the Information Schema database) and views on the server.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
TABLE_TYPEOne of BASE TABLE for a regular table, VIEW for a view, SYSTEM VIEW for Information Schema tables, SYSTEM VERSIONED for system-versioned tables or SEQUENCE for sequences.
ENGINEStorage Engine.
VERSIONVersion number from the table's .frm file
ROW_FORMATRow format (see InnoDB, Aria and MyISAM row formats).
TABLE_ROWSNumber of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate.
AVG_ROW_LENGTHAverage row length in the table.
DATA_LENGTHFor InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory.
MAX_DATA_LENGTHMaximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB.
INDEX_LENGTHLength of the index file.
DATA_FREEBytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table.
AUTO_INCREMENTNext AUTO_INCREMENT value.
CREATE_TIMETime the table was created.
UPDATE_TIMETime the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE.
CHECK_TIMETime the table was last checked. Not kept by all storage engines, in which case will be NULL.
TABLE_COLLATIONCharacter set and collation.
CHECKSUMLive checksum value, if any.
CREATE_OPTIONSExtra CREATE TABLE options.
TABLE_COMMENTTable comment provided when MariaDB created the table.
MAX_INDEX_LENGTHMaximum index length (supported by MyISAM and Aria tables). Added in MariaDB 10.3.5.
TEMPORARYPlaceholder to signal that a table is a temporary table. Currently always "N", except "Y" for generated information_schema tables and NULL for views. Added in MariaDB 10.3.5.

Although the table is standard in the Information Schema, all but TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE and VERSION are MySQL and MariaDB extensions.

SHOW TABLES lists all tables in a database.

Examples

From MariaDB 10.3.5:

SELECT * FROM information_schema.tables WHERE table_schema='test'\G
*************************** 1. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: test
      TABLE_NAME: xx5
      TABLE_TYPE: BASE TABLE
          ENGINE: InnoDB
         VERSION: 10
      ROW_FORMAT: Dynamic
      TABLE_ROWS: 0
  AVG_ROW_LENGTH: 0
     DATA_LENGTH: 16384
 MAX_DATA_LENGTH: 0
    INDEX_LENGTH: 0
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-18 15:57:10
     UPDATE_TIME: NULL
      CHECK_TIME: NULL
 TABLE_COLLATION: latin1_swedish_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: 
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 0
       TEMPORARY: N
*************************** 2. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: test
      TABLE_NAME: xx4
      TABLE_TYPE: BASE TABLE
          ENGINE: MyISAM
         VERSION: 10
      ROW_FORMAT: Fixed
      TABLE_ROWS: 0
  AVG_ROW_LENGTH: 0
     DATA_LENGTH: 0
 MAX_DATA_LENGTH: 1970324836974591
    INDEX_LENGTH: 1024
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-18 15:56:57
     UPDATE_TIME: 2020-11-18 15:56:57
      CHECK_TIME: NULL
 TABLE_COLLATION: latin1_swedish_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: 
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 17179868160
       TEMPORARY: N
...

Example with temporary = 'y', from MariaDB 10.3.5:

SELECT * FROM information_schema.tables WHERE temporary='y'\G
 *************************** 1. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: information_schema
      TABLE_NAME: INNODB_FT_DELETED
      TABLE_TYPE: SYSTEM VIEW
          ENGINE: MEMORY
         VERSION: 11
      ROW_FORMAT: Fixed
      TABLE_ROWS: NULL
  AVG_ROW_LENGTH: 9
     DATA_LENGTH: 0
 MAX_DATA_LENGTH: 9437184
    INDEX_LENGTH: 0
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-17 21:54:02
     UPDATE_TIME: NULL
      CHECK_TIME: NULL
 TABLE_COLLATION: utf8_general_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: max_rows=1864135
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 0
       TEMPORARY: Y
...

View Tables in Order of Size

Returns a list of all tables in the database, ordered by size:

SELECT table_schema as `DB`, table_name AS `Table`, 
  ROUND(((data_length + index_length) / 1024 / 1024), 2) `Size (MB)` 
  FROM information_schema.TABLES 
  ORDER BY (data_length + index_length) DESC;

+--------------------+---------------------------------------+-----------+
| DB                 | Table                                 | Size (MB) |
+--------------------+---------------------------------------+-----------+
| wordpress          | wp_simple_history_contexts            |      7.05 |
| wordpress          | wp_posts                              |      6.59 |
| wordpress          | wp_simple_history                     |      3.05 |
| wordpress          | wp_comments                           |      2.73 |
| wordpress          | wp_commentmeta                        |      2.47 |
| wordpress          | wp_simple_login_log                   |      2.03 |
...

See Also

1.1.2.9.1.1.51 Information Schema TABLESPACES Table

The Information Schema TABLESPACES table contains information about active tablespaces..

The table is a MariaDB and MySQL extension, and does not include information about InnoDB tablespaces.

ColumnDescription
TABLESPACE_NAME
ENGINE
TABLESPACE_TYPE
LOGFILE_GROUP_NAME
EXTENT_SIZE
AUTOEXTEND_SIZE
MAXIMUM_SIZE
NODEGROUP_ID
TABLESPACE_COMMENT

1.1.2.9.1.1.52 Information Schema THREAD_POOL_GROUPS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_GROUPS table was introduced in MariaDB 10.5.0.

The table provides information about thread pool groups, and contains the following columns:

ColumnDescription
GROUP_ID
CONNECTIONS
THREADS
ACTIVE_THREADS
STANDBY_THREADS
QUEUE_LENGTH
HAS_LISTENER
IS_STALLED

Setting thread_pool_dedicated_listener will give each group its own dedicated listener, and the listener thread will not pick up work items. As a result, the actual queue size in the table will be more exact, since IO requests are immediately dequeued from poll, without delay.

1.1.2.9.1.1.53 Information Schema THREAD_POOL_STATS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_STATS table was introduced in MariaDB 10.5.0.

The table provides performance counter information for the thread pool, and contains the following columns:

ColumnDescription
GROUP_ID
THREAD_CREATIONS
THREAD_CREATIONS_DUE_TO_STALL
WAKES
WAKES_DUE_TO_STALL
THROTTLES
STALLS
POLLS_BY_LISTENER
POLLS_BY_WORKER
DEQUEUES_BY_LISTENER
DEQUEUES_BY_WORKER

1.1.2.9.1.1.54 Information Schema THREAD_POOL_WAITS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_WAITS table was introduced in MariaDB 10.5.0.

The table provides wait counters for the thread pool, and contains the following columns:

ColumnDescription
REASON
COUNT

1.1.2.9.1.1.55 Information Schema TRIGGERS Table

Contents

  1. See also

The Information Schema TRIGGERS table contains information about triggers.

It has the following columns:

ColumnDescription
TRIGGER_CATALOGAlways def.
TRIGGER_SCHEMADatabase name in which the trigger occurs.
TRIGGER_NAMEName of the trigger.
EVENT_MANIPULATIONThe event that activates the trigger. One of INSERT, UPDATE or 'DELETE.
EVENT_OBJECT_CATALOGAlways def.
EVENT_OBJECT_SCHEMADatabase name on which the trigger acts.
EVENT_OBJECT_TABLETable name on which the trigger acts.
ACTION_ORDERIndicates the order that the action will be performed in (of the list of a table's triggers with identical EVENT_MANIPULATION and ACTION_TIMING values). Before MariaDB 10.2.3 introduced the FOLLOWS and PRECEDES clauses, always 0
ACTION_CONDITIONNULL
ACTION_STATEMENTTrigger body, UTF-8 encoded.
ACTION_ORIENTATIONAlways ROW.
ACTION_TIMINGWhether the trigger acts BEFORE or AFTER the event that triggers it.
ACTION_REFERENCE_OLD_TABLEAlways NULL.
ACTION_REFERENCE_NEW_TABLEAlways NULL.
ACTION_REFERENCE_OLD_ROWAlways OLD.
ACTION_REFERENCE_NEW_ROWAlways NEW.
CREATEDAlways NULL.
SQL_MODEThe SQL_MODE when the trigger was created, and which it uses for execution.
DEFINERThe account that created the trigger, in the form user_name@host_name
CHARACTER_SET_CLIENTThe client character set when the trigger was created, from the session value of the character_set_client system variable.
COLLATION_CONNECTIONThe client collation when the trigger was created, from the session value of the collation_connection system variable.
DATABASE_COLLATIONCollation of the associated database.

Queries to the TRIGGERS table will return information only for databases and tables for which you have the TRIGGER privilege. Similar information is returned by the SHOW TRIGGERS statement.

See also

1.1.2.9.1.1.56 Information Schema USER_PRIVILEGES Table

The Information Schema USER_PRIVILEGES table contains global user privilege information derived from the mysql.user grant table.

It contains the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
PRIVILEGE_TYPEThe specific privilege, for example SELECT, INSERT, UPDATE or REFERENCES.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW GRANTS statement. See the GRANT article for more about privileges.

This information is also stored in the user table, in the mysql system database.

1.1.2.9.1.1.57 Information Schema USER_STATISTICS Table

The Information Schema USER_STATISTICS table holds statistics about user activity. This is part of the User Statistics feature, which is not enabled by default.

You can use this table to find out such things as which user is causing the most load and which users are being abusive. You can also use this table to measure how close to capacity the server may be.

It contains the following columns:

FieldTypeNotes
USERvarchar(48)The username. The value '#mysql_system_user#' appears when there is no username (such as for the slave SQL thread).
TOTAL_CONNECTIONSint(21)The number of connections created for this user.
CONCURRENT_CONNECTIONSint(21)The number of concurrent connections for this user.
CONNECTED_TIMEint(21)The cumulative number of seconds elapsed while there were connections from this user.
BUSY_TIMEdoubleThe cumulative number of seconds there was activity on connections from this user.
CPU_TIMEdoubleThe cumulative CPU time elapsed while servicing this user's connections.
BYTES_RECEIVEDint(21)The number of bytes received from this user's connections.
BYTES_SENTint(21)The number of bytes sent to this user's connections.
BINLOG_BYTES_WRITTENint(21)The number of bytes written to the binary log from this user's connections.
ROWS_READint(21)The number of rows read by this user's connections.
ROWS_SENTint(21)The number of rows sent by this user's connections.
ROWS_DELETEDint(21)The number of rows deleted by this user's connections.
ROWS_INSERTEDint(21)The number of rows inserted by this user's connections.
ROWS_UPDATEDint(21)The number of rows updated by this user's connections.
SELECT_COMMANDSint(21)The number of SELECT commands executed from this user's connections.
UPDATE_COMMANDSint(21)The number of UPDATE commands executed from this user's connections.
OTHER_COMMANDSint(21)The number of other commands executed from this user's connections.
COMMIT_TRANSACTIONSint(21)The number of COMMIT commands issued by this user's connections.
ROLLBACK_TRANSACTIONSint(21)The number of ROLLBACK commands issued by this user's connections.
DENIED_CONNECTIONSint(21)The number of connections denied to this user.
LOST_CONNECTIONSint(21)The number of this user's connections that were terminated uncleanly.
ACCESS_DENIEDint(21)The number of times this user's connections issued commands that were denied.
EMPTY_QUERIESint(21)The number of times this user's connections sent empty queries to the server.
TOTAL_SSL_CONNECTIONSint(21)The number of TLS connections created for this user. (>= MariaDB 10.1.1)
MAX_STATEMENT_TIME_EXCEEDEDint(21)The number of times a statement was aborted, because it was executed longer than its MAX_STATEMENT_TIME threshold. (>= MariaDB 10.1.1)

Example

SELECT * FROM information_schema.USER_STATISTICS\G
*************************** 1. row ***************************
                  USER: root
     TOTAL_CONNECTIONS: 1
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 297
             BUSY_TIME: 0.001725
              CPU_TIME: 0.001982
        BYTES_RECEIVED: 388
            BYTES_SENT: 2327
  BINLOG_BYTES_WRITTEN: 0
             ROWS_READ: 0
             ROWS_SENT: 12
          ROWS_DELETED: 0
         ROWS_INSERTED: 13
          ROWS_UPDATED: 0
       SELECT_COMMANDS: 4
       UPDATE_COMMANDS: 0
        OTHER_COMMANDS: 3
   COMMIT_TRANSACTIONS: 0
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 1

1.1.2.9.1.1.58 Information Schema USER_VARIABLES Table

MariaDB 10.2.0

The USER_VARIABLES table was introduced in MariaDB 10.2.0 as part of the user_variables plugin.

Description

The USER_VARIABLES table is created when the user_variables plugin is enabled, and contains information about user-defined variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEVariable name.
VARIABLE_VALUEVariable value.
VARIABLE_TYPEVariable type.
CHARACTER_SET_NAMECharacter set.

Example

SELECT * FROM information_schema.USER_VARIABLES ORDER BY VARIABLE_NAME;
+---------------+----------------+---------------+--------------------+
| VARIABLE_NAME | VARIABLE_VALUE | VARIABLE_TYPE | CHARACTER_SET_NAME |
+---------------+----------------+---------------+--------------------+
| var           | 0              | INT           | utf8               |
| var2          | abc            | VARCHAR       | utf8               |
+---------------+----------------+---------------+--------------------+

1.1.2.9.1.1.59 Information Schema VIEWS Table

The Information Schema VIEWS table contains information about views. The SHOW VIEW privilege is required to view the table.

It has the following columns:

ColumnDescriptionAdded
TABLE_CATALOGAways def.
TABLE_SCHEMADatabase name containing the view.
TABLE_NAMEView table name.
VIEW_DEFINITIONDefinition of the view.
CHECK_OPTIONYES if the WITH CHECK_OPTION clause has been specified, NO otherwise.
IS_UPDATABLEWhether the view is updatable or not.
DEFINERAccount specified in the DEFINER clause (or the default when created).
SECURITY_TYPESQL SECURITY characteristic, either DEFINER or INVOKER.
CHARACTER_SET_CLIENTThe client character set when the view was created, from the session value of the character_set_client system variable.
COLLATION_CONNECTIONThe client collation when the view was created, from the session value of the collation_connection system variable.
ALGORITHMThe algorithm used in the view. See View Algorithms.MariaDB 10.1.3

Example

SELECT * FROM information_schema.VIEWS\G
*************************** 1. row ***************************
       TABLE_CATALOG: def
        TABLE_SCHEMA: test
          TABLE_NAME: v
     VIEW_DEFINITION: select `test`.`t`.`qty` AS `qty`,`test`.`t`.`price` AS `price`,(`test`.`t`.`qty` * `test`.`t`.`price`) AS `value` from `test`.`t`
        CHECK_OPTION: NONE
        IS_UPDATABLE: YES
             DEFINER: root@localhost
       SECURITY_TYPE: DEFINER
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
           ALGORITHM: UNDEFINED

See also

1.1.2.9.1.1.60 Information Schema WSREP_MEMBERSHIP Table

The WSREP_STATUS table makes Galera node cluster membership information available through the Information Schema. The same information can be returned using the SHOW WSREP_MEMBERSHIP statement. Only users with the SUPER can access information from this table.

The WSREP_MEMBERSHIP table is part of the WSREP_INFO plugin.

Example

SELECT * FROM information_schema.WSREP_MEMBERSHIP;
+-------+--------------------------------------+-------+-----------------+
| INDEX | UUID                                 | NAME  | ADDRESS         |
+-------+--------------------------------------+-------+-----------------+
|     0 | 46da96e3-6e9e-11e4-95a2-f609aa5444b3 | node1 | 10.0.2.15:16000 |
|     1 | 5f6bc72a-6e9e-11e4-84ed-57ec6780a3d3 | node2 | 10.0.2.15:16001 |
|     2 | 7473fd75-6e9e-11e4-91de-0b541ad91bd0 | node3 | 10.0.2.15:16002 |
+-------+--------------------------------------+-------+-----------------+

1.1.2.9.1.1.61 Information Schema WSREP_STATUS Table

The WSREP_STATUS table makes Galera node cluster status information available through the Information Schema. The same information can be returned using the SHOW WSREP_STATUS statement. Only users with the SUPER privilege can access information from this table.

The WSREP_STATUS table is part of the WSREP_INFO plugin.

Example

SELECT * FROM information_schema.WSREP_STATUS\G
*************************** 1. row ***************************
         NODE_INDEX: 0
        NODE_STATUS: Synced
     CLUSTER_STATUS: Primary
       CLUSTER_SIZE: 3
 CLUSTER_STATE_UUID: 00b0fbad-6e84-11e4-8a8b-376f19ce8ee7
CLUSTER_STATE_SEQNO: 2
    CLUSTER_CONF_ID: 3
                GAP: NO
   PROTOCOL_VERSION: 3

1.1.2.9.1.2

1.1.2.9.1.3 TIME_MS column in INFORMATION_SCHEMA.PROCESSLIST

In MariaDB, an extra column TIME_MS has been added to the INFORMATION_SCHEMA.PROCESSLIST table. This column shows the same information as the column 'TIME', but in units of milliseconds with microsecond precision (the unit and precision of the TIME column is one second).

For details about microseconds support in MariaDB, see microseconds in MariaDB.

The value displayed in the TIME and TIME_MS columns is the period of time that the given thread has been in its current state. Thus it can be used to check for example how long a thread has been executing the current query, or for how long it has been idle.

select id, time, time_ms, command, state from
   information_schema.processlist, (select sleep(2)) t;
+----+------+----------+---------+-----------+
| id | time | time_ms  | command | state     |
+----+------+----------+---------+-----------+
| 37 |    2 | 2000.493 | Query   | executing |
+----+------+----------+---------+-----------+

Note that as a difference to MySQL, in MariaDB the TIME column (and also the TIME_MS column) are not affected by any setting of @TIMESTAMP. This means that it can be reliably used also for threads that change @TIMESTAMP (such as the replication SQL thread). See also MySQL Bug #22047.

As a consequence of this, the TIME column of SHOW FULL PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST can not be used to determine if a slave is lagging behind. For this, use instead the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS.

The addition of the TIME_MS column is based on the microsec_process patch, developed by Percona.

1.1.2.9.2 Performance Schema

1.1.2.9.2.1 Performance Schema Tables

1.1.2.9.2.1.1 List of Performance Schema Tables

Below is a list of all Performance Schema tables as well as a brief description of each of them.

TableDescription
accountsClient account connection statistics.
cond_instancesSynchronization object instances.
events_stages_currentCurrent stage events.
events_stages_historyTen most recent stage events per thread.
events_stages_history_longTen thousand most recent stage events.
events_stages_summary_by_account_by_event_nameSummarized stage events per account and event name.
events_stages_summary_by_host_by_event_nameSummarized stage events per host and event name.
events_stages_summary_by_thread_by_event_nameSummarized stage events per thread and event name.
events_stages_summary_by_user_by_event_nameSummarized stage events per user name and event name.
events_stages_summary_global_by_event_nameSummarized stage events per event name.
events_statements_currentCurrent statement events.
events_statements_historyTen most recent events per thread.
events_statements_history_longTen thousand most recent stage events.
events_statements_summary_by_account_by_event_nameSummarized statement events per account and event name.
events_statements_summary_by_digestSummarized statement events by scheme and digest.
events_statements_summary_by_host_by_event_nameSummarized statement events by host and event name.
events_statements_summary_by_program
events_statements_summary_by_thread_by_event_nameSummarized statement events by thread and event name.
events_statements_summary_by_user_by_event_nameSummarized statement events by user and event name.
events_statements_summary_global_by_event_nameSummarized statement events by event name.
events_transactions_currentCurrent transaction events for each thread.
events_transactions_historyMost recent completed transaction events for each thread.
events_transactions_history_longMost recent completed transaction events that have ended globally.
events_transactions_summary_by_account_by_event_nameTransaction events aggregated by account and event.
events_transactions_summary_by_host_by_event_nameTransaction events aggregated by host and event..
events_transactions_summary_by_thread_by_event_nameTransaction events aggregated by thread and event..
events_transactions_summary_by_user_by_event_nameTransaction events aggregated by user and event..
events_transactions_summary_global_by_event_nameTransaction events aggregated by event name.
events_waits_currentCurrent wait events.
events_waits_historyTen most recent wait events per thread.
events_waits_history_longTen thousand most recent wait events per thread.
events_waits_summary_by_account_by_event_nameSummarized wait events by account and event name.
events_waits_summary_by_host_by_event_nameSummarized wait events by host and event name.
events_waits_summary_by_instanceSummarized wait events by instance.
events_waits_summary_by_thread_by_event_nameSummarized wait events by thread and event name.
events_waits_summary_by_user_by_event_nameSummarized wait events by user and event name.
events_waits_summary_global_by_event_nameSummarized wait events by event name.
file_instancesSeen files.
file_summary_by_event_nameFile events summarized by event name.
file_summary_by_instanceFile events summarized by instance.
global_statusGlobal status variables and values.
host_cacheHost and IP information.
hostsConnections by host.
memory_summary_by_account_by_event_nameMemory usage statistics aggregated by account and event.
memory_summary_by_host_by_event_nameMemory usage statistics aggregated by host. and event.
memory_summary_by_thread_by_event_nameMemory usage statistics aggregated by thread and event..
memory_summary_by_user_by_event_nameMemory usage statistics aggregated by user and event..
memory_summary_global_by_event_nameMemory usage statistics aggregated by event.
metadata_locksMetadata locks.
mutex_instancesSeen mutexes.
objects_summary_global_by_typeObject wait events.
performance_timersAvailable event timers.
prepared_statements_instancesAggregate statistics of prepared statements.
replication_applier_configurationConfiguration settings affecting replica transactions.
replication_applier_statusGeneral transaction execution status on the replica.
replication_applier_status_by_coordinatorCoordinator thread specific information.
replication_applier_status_by_workerReplica worker thread specific information.
replication_connection_configurationRreplica's configuration settings used for connecting to the primary.
rwlock_instancesSeen read-write locks.
session_account_connect_attrsCurrent session connection attributes.
session_connect_attrsAll session connection attributes.
session_statusSession status variables and values.
setup_actorsDetails on foreground thread monitoring.
setup_consumersConsumers for which event information is stored.
setup_instrumentsInstrumented objects for which events are collected.
setup_objectsObjects to be monitored.
setup_timersCurrently selected event timers.
socket_instancesActive connections.
socket_summary_by_event_nameTimer and byte count statistics by socket instrument.
socket_summary_by_instanceTimer and byte count statistics by socket instance.
status_by_threadStatus variable info about active foreground threads.
table_io_waits_summary_by_index_usageAggregate table I/O wait events by index.
table_io_waits_summary_by_tableAggregate table I/O wait events by table.
table_lock_waits_summary_by_tableAggregate table lock wait events by table.
threadsServer thread information.
usersConnection statistics by user.

1.1.2.9.2.1.2 Performance Schema accounts Table

Description

Each account that connects to the server is stored as a row in the accounts table, along with current and total connections.

The table size is determined at startup by the value of the performance_schema_accounts_size system variable. If this is set to 0, account statistics will be disabled.

ColumnDescription
USERThe connection's client user name for the connection, or NULL if an internal thread.
HOSTThe connection client's host name, or NULL if an internal thread.
CURRENT_CONNECTIONSCurrent connections for the account.
TOTAL_CONNECTIONSTotal connections for the account.

The USER and HOST values shown here are the username and host used for user connections, not the patterns used to check permissions.

Example

SELECT * FROM performance_schema.accounts;
+------------------+-----------+---------------------+-------------------+
| USER             | HOST      | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+-----------+---------------------+-------------------+
| root             | localhost |                   1 |                 2 |
| NULL             | NULL      |                  20 |                23 |
| debian-sys-maint | localhost |                   0 |                35 |
+------------------+-----------+---------------------+-------------------+

1.1.2.9.2.1.3 Performance Schema cond_instances Table

Description

The cond_instances table lists all conditions while the server is executing. A condition, or instrumented condition object, is an internal code mechanism used for signalling that a specific event has occurred so that any threads waiting for this condition can continue.

The maximum number of conditions stored in the performance schema is determined by the performance_schema_max_cond_instances system variable.

ColumnDescription
NAMEClient user name for the connection, or NULL if an internal thread.
OBJECT_INSTANCE_BEGINAddress in memory of the instrumented condition.

1.1.2.9.2.1.4 Performance Schema events_stages_current Table

The events_stages_current table contains current stage events, with each row being a record of a thread and its most recent stage event.

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if the event has not ended or timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if the event has not ended or timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

The related tables, events_stages_history and events_stages_history_long derive their values from the current events.

1.1.2.9.2.1.5 Performance Schema events_stages_history Table

The events_stages_history table by default contains the ten most recent completed stage events per thread. This number can be adjusted by setting the performance_schema_events_stages_history_size system variable when the server starts up.

The table structure is identical to the events_stage_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_stages_current and events_stages_history_long are related tables.

1.1.2.9.2.1.6 Performance Schema events_stages_history_long Table

The events_stages_history_long table by default contains the ten thousand most recent completed stage events. This number can be adjusted by setting the performance_schema_events_stages_history_long_size system variable when the server starts up.

The table structure is identical to the events_stage_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_stages_current and events_stages_history are related tables.

1.1.2.9.2.1.7 Performance Schema events_stages_summary_by_account_by_event_name Table

The table lists stage events, summarized by account and event name.

It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_account_by_event_name\G
...
*************************** 325. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 326. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 327. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.8 Performance Schema events_stages_summary_by_host_by_event_name Table

The table lists stage events, summarized by host and event name.

It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with HOST for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_host_by_event_name\G
...
*************************** 216. row ***************************
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 217. row ***************************
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 218. row ***************************
          HOST: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.9 Performance Schema events_stages_summary_by_thread_by_event_name Table

The table lists stage events, summarized by thread and event name.

It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_thread_by_event_name\G
...
*************************** 2287. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 2288. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 2289. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.10 Performance Schema events_stages_summary_by_user_by_event_name Table

The table lists stage events, summarized by user and event name.

It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_user_by_event_name\G
...
*************************** 325. row ***************************
          USER: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 326. row ***************************
          USER: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 327. row ***************************
          USER: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.11 Performance Schema events_stages_summary_global_by_event_name Table

The table lists stage events, summarized by thread and event name.

It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_global_by_event_name\G
...
*************************** 106. row ***************************
    EVENT_NAME: stage/sql/Waiting for trigger metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 107. row ***************************
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 108. row ***************************
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 109. row ***************************
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.12 Performance Schema events_statements_history Table

The events_statements_history table by default contains the ten most recent completed statement events per thread. This number can be adjusted by setting the performance_schema_events_statements_history_size system variable when the server starts up.

The table structure is identical to the events_statements_current table structure, and contains the following columns:

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
LOCK_TIMETime in picoseconds spent waiting for locks. The time is calculated in microseconds but stored in picoseconds for compatibility with other timings.
SQL_TEXTThe SQL statement, or NULL if the command is not associated with an SQL statement.
DIGESTStatement digest.
DIGEST_TEXTStatement digest text.
CURRENT_SCHEMAStatement's default database for the statement, or NULL if there was none.
OBJECT_SCHEMAReserved, currently NULL
OBJECT_NAMEReserved, currently NULL
OBJECT_TYPEReserved, currently NULL
OBJECT_INSTANCE_BEGINAddress in memory of the statement object.
MYSQL_ERRNOError code. See MariaDB Error Codes for a full list.
RETURNED_SQLSTATEThe SQLSTATE value.
MESSAGE_TEXTStatement error message. See MariaDB Error Codes.
ERRORS0 if SQLSTATE signifies completion (starting with 00) or warning (01), otherwise 1.
WARNINGSNumber of warnings from the diagnostics area.
ROWS_AFFECTEDNumber of rows affected the statement affected.
ROWS_SENTNumber of rows returned.
ROWS_EXAMINEDNumber of rows read during the statement's execution.
CREATED_TMP_DISK_TABLESNumber of on-disk temp tables created by the statement.
CREATED_TMP_TABLESNumber of temp tables created by the statement.
SELECT_FULL_JOINNumber of joins performed by the statement which did not use an index.
SELECT_FULL_RANGE_JOINNumber of joins performed by the statement which used a range search of the first table.
SELECT_RANGENumber of joins performed by the statement which used a range of the first table.
SELECT_RANGE_CHECKNumber of joins without keys performed by the statement that check for key usage after each row.
SELECT_SCANNumber of joins performed by the statement which used a full scan of the first table.
SORT_MERGE_PASSESNumber of merge passes by the sort algorithm performed by the statement. If too high, you may need to increase the sort_buffer_size.
SORT_RANGENumber of sorts performed by the statement which used a range.
SORT_ROWSNumber of rows sorted by the statement.
SORT_SCANNumber of sorts performed by the statement which used a full table scan.
NO_INDEX_USED0 if the statement performed a table scan with an index, 1 if without an index.
NO_GOOD_INDEX_USED0 if a good index was found for the statement, 1 if no good index was found. See the Range checked for each record description in the EXPLAIN article.
NESTING_EVENT_IDReserved, currently NULL.
NESTING_EVENT_TYPEReserved, currently NULL.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_statements_current and events_statements_history_long are related tables.

1.1.2.9.2.1.13 Performance Schema events_statements_history_long Table

The events_statements_history_long table by default contains the ten thousand most recent completed statement events. This number can be adjusted by setting the performance_schema_events_statements_history_long_size system variable when the server starts up.

The table structure is identical to the events_statements_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
LOCK_TIMETime in picoseconds spent waiting for locks. The time is calculated in microseconds but stored in picoseconds for compatibility with other timings.
SQL_TEXTThe SQL statement, or NULL if the command is not associated with an SQL statement.
DIGESTStatement digest.
DIGEST_TEXTStatement digest text.
CURRENT_SCHEMAStatement's default database for the statement, or NULL if there was none.
OBJECT_SCHEMAReserved, currently NULL
OBJECT_NAMEReserved, currently NULL
OBJECT_TYPEReserved, currently NULL
OBJECT_INSTANCE_BEGINAddress in memory of the statement object.
MYSQL_ERRNOError code. See MariaDB Error Codes for a full list.
RETURNED_SQLSTATEThe SQLSTATE value.
MESSAGE_TEXTStatement error message. See MariaDB Error Codes.
ERRORS0 if SQLSTATE signifies completion (starting with 00) or warning (01), otherwise 1.
WARNINGSNumber of warnings from the diagnostics area.
ROWS_AFFECTEDNumber of rows affected the statement affected.
ROWS_SENTNumber of rows returned.
ROWS_EXAMINEDNumber of rows read during the statement's execution.
CREATED_TMP_DISK_TABLESNumber of on-disk temp tables created by the statement.
CREATED_TMP_TABLESNumber of temp tables created by the statement.
SELECT_FULL_JOINNumber of joins performed by the statement which did not use an index.
SELECT_FULL_RANGE_JOINNumber of joins performed by the statement which used a range search of the first table.
SELECT_RANGENumber of joins performed by the statement which used a range of the first table.
SELECT_RANGE_CHECKNumber of joins without keys performed by the statement that check for key usage after each row.
SELECT_SCANNumber of joins performed by the statement which used a full scan of the first table.
SORT_MERGE_PASSESNumber of merge passes by the sort algorithm performed by the statement. If too high, you may need to increase the sort_buffer_size.
SORT_RANGENumber of sorts performed by the statement which used a range.
SORT_ROWSNumber of rows sorted by the statement.
SORT_SCANNumber of sorts performed by the statement which used a full table scan.
NO_INDEX_USED0 if the statement performed a table scan with an index, 1 if without an index.
NO_GOOD_INDEX_USED0 if a good index was found for the statement, 1 if no good index was found. See the Range checked for each record description in the EXPLAIN article.
NESTING_EVENT_IDReserved, currently NULL.
NESTING_EVENT_TYPEReserved, currently NULL.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_statements_current and events_statements_history are related tables.

1.1.2.9.2.1.14 Performance Schema events_statements_summary_by_account_by_event_name Table

The Performance Schema events_statements_summary_by_account_by_event_name table contains statement events summarized by account and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_account_by_event_name\G
...
*************************** 521. row ***************************
                       USER: NULL
                       HOST: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 522. row ***************************
                       USER: NULL
                       HOST: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.2.9.2.1.15 Performance Schema events_statements_summary_by_digest Table

The Performance Schema digest is a hashed, normalized form of a statement with the specific data values removed. It allows statistics to be gathered for similar kinds of statements.

The Performance Schema events_statements_summary_by_digest table records statement events summarized by schema and digest. It contains the following columns:

ColumnDescription
SCHEMA NAMEDatabase name. Records are summarised together with DIGEST.
DIGESTPerformance Schema digest. Records are summarised together with SCHEMA NAME.
DIGEST TEXTThe unhashed form of the digest.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.
FIRST_SEENTime at which the digest was first seen.
LAST_SEENTime at which the digest was most recently seen.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

The events_statements_summary_by_digest table is limited in size by the performance_schema_digests_size system variable. Once the limit has been reached and the table is full, all entries are aggregated in a row with a NULL digest. The COUNT_STAR value of this NULL row indicates how many digests are recorded in the row and therefore gives an indication of whether performance_schema_digests_size should be increased to provide more accurate statistics.

1.1.2.9.2.1.16 Performance Schema events_statements_summary_by_host_by_event_name Table

The Performance Schema events_statements_summary_by_host_by_event_name table contains statement events summarized by host and event name. It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_currentd table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOINW column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_host_by_event_name\G
...
*************************** 347. row ***************************
                       HOST: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 348. row ***************************
                       HOST: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.2.9.2.1.17 Performance Schema events_statements_summary_by_program Table

MariaDB starting with 10.5.2

The events_statements_summary_by_program table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

Each row in the the Performance Schema events_statements_summary_by_program table summarizes events for a particular stored program (stored procedure, stored function, trigger or event).

It contains the following fields.

ColumnTypeNullDescription
OBJECT_TYPEenum('EVENT', 'FUNCTION', 'PROCEDURE', 'TABLE', 'TRIGGER')YESObject type for which the summary is generated.
OBJECT_SCHEMAvarchar(64)NOThe schema of the object for which the summary is generated.
OBJECT_NAMEvarchar(64)NOThe name of the object for which the summary is generated.
COUNT_STARbigint(20) unsignedNOThe number of summarized events (from events_statements_current). This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedNOThe number of summarized events (from events_statements_current). This value includes all events, whether timed or nontimed.
MIN_TIMER_WAITbigint(20) unsignedNOThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedNOThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedNOThe maximum wait time of the summarized timed events.
COUNT_STATEMENTSbigint(20) unsignedNOTotal number of nested statements invoked during stored program execution.
SUM_STATEMENTS_WAITbigint(20) unsignedNOThe total wait time of the summarized timed statements. This value is calculated only for timed statements because nontimed statements have a wait time of NULL. The same is true for the other xxx_STATEMENT_WAIT values.
MIN_STATEMENTS_WAITbigint(20) unsignedNOThe minimum wait time of the summarized timed statements.
AVG_STATEMENTS_WAITbigint(20) unsignedNOThe average wait time of the summarized timed statements.
MAX_STATEMENTS_WAITbigint(20) unsignedNOThe maximum wait time of the summarized timed statements.
SUM_LOCK_TIMEbigint(20) unsignedNOThe total time spent (in picoseconds) waiting for table locks for the summarized statements.
SUM_ERRORSbigint(20) unsignedNOThe total number of errors that occurend for the summarized statements.
SUM_WARNINGSbigint(20) unsignedNOThe total number of warnings that occurend for the summarized statements.
SUM_ROWS_AFFECTEDbigint(20) unsignedNOThe total number of affected rows by the summarized statements.
SUM_ROWS_SENTbigint(20) unsignedNOThe total number of rows returned by the summarized statements.
SUM_ROWS_EXAMINEDbigint(20) unsignedNOThe total number of rows examined by the summarized statements.The total number of affected rows by the summarized statements.
SUM_CREATED_TMP_DISK_TABLESbigint(20) unsignedNOThe total number of on-disk temporary tables created by the summarized statements.
SUM_CREATED_TMP_TABLESbigint(20) unsignedNOThe total number of in-memory temporary tables created by the summarized statements.
SUM_SELECT_FULL_JOINbigint(20) unsignedNOThe total number of full joins executed by the summarized statements.
SUM_SELECT_FULL_RANGE_JOINbigint(20) unsignedNOThe total number of range search joins executed by the summarized statements.
SUM_SELECT_RANGEbigint(20) unsignedNOThe total number of joins that used ranges on the first table executed by the summarized statements.
SUM_SELECT_RANGE_CHECKbigint(20) unsignedNOThe total number of joins that check for key usage after each row executed by the summarized statements.
SUM_SELECT_SCANbigint(20) unsignedNOThe total number of joins that did a full scan of the first table executed by the summarized statements.
SUM_SORT_MERGE_PASSESbigint(20) unsignedNOThe total number of merge passes that the sort algorithm has had to do for the summarized statements.
SUM_SORT_RANGEbigint(20) unsignedNOThe total number of sorts that were done using ranges for the summarized statements.
SUM_SORT_ROWSbigint(20) unsignedNOThe total number of sorted rows that were sorted by the summarized statements.
SUM_SORT_SCANbigint(20) unsignedNOThe total number of sorts that were done by scanning the table by the summarized statements.
SUM_NO_INDEX_USEDbigint(20) unsignedNOThe total number of statements that performed a table scan without using an index.
SUM_NO_GOOD_INDEX_USEDbigint(20) unsignedNOThe total number of statements where no good index was found.

1.1.2.9.2.1.18 Performance Schema events_statements_summary_by_thread_by_event_name Table

The Performance Schema events_statements_summary_by_thread_by_event_name table contains statement events summarized by thread and event name. It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_thread_by_event_name\G
...
*************************** 3653. row ***************************
                  THREAD_ID: 64
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 3654. row ***************************
                  THREAD_ID: 64
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.2.9.2.1.19 Performance Schema events_statements_summary_by_user_by_event_name Table

The Performance Schema events_statements_summary_by_user_by_event_name table contains statement events summarized by user and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_user_by_event_name\G
...
*************************** 521. row ***************************
                       USER: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 522. row ***************************
                       USER: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.2.9.2.1.20 Performance Schema events_statements_summary_global_by_event_name Table

The Performance Schema events_statements_summary_global_by_event_name table contains statement events summarized by event name. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_global_by_event_name\G
...
*************************** 173. row ***************************
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 174. row ***************************
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.2.9.2.1.21 Performance Schema events_transactions_current Table

MariaDB starting with 10.5.2

The events_transactions_current table was introduced in MariaDB 10.5.2.

The events_transactions_current table contains current transaction events for each thread.

The table size cannot be figured, and always stores one row for each thread, showing the current status of the thread's most recent monitored transaction event.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED', 'ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES','NO')Whether autcommit mode was enabled when the transaction started.
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION', 'STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.2.9.2.1.22 Performance Schema events_transactions_history Table

MariaDB starting with 10.5.2

The events_transactions_history table was introduced in MariaDB 10.5.2.

The events_transactions_history table contains the most recent completed transaction events for each thread.

The number of records stored per thread in the table is determined by the performance_schema_events_transactions_history_size system variable, which is autosized on startup.

If adding a completed transaction event would cause the table to exceed this limit, the oldest thread row is discarded.

All of a thread's rows are discarded when the thread ends.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED',' ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES', 'NO')NO
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION',' STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.2.9.2.1.23 Performance Schema events_transactions_history_long Table

MariaDB starting with 10.5.2

The events_transactions_history_long table was introduced in MariaDB 10.5.2.

The events_transactions_history_long table contains the most recent completed transaction events that have ended globally, across all threads.

The number of records stored in the table is determined by the performance_schema_events_transactions_history_long_size system variable, which is autosized on startup.

If adding a completed transaction would cause the table to exceed this limit, the oldest row, regardless of thread, is discarded.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED',' ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES', 'NO')NO
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION',' STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.2.9.2.1.24 Performance Schema events_transactions_summary_by_account_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_account_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_account_by_event_name table contains information on transaction events aggregated by account and event name.

The table contains the following columns:

ColumnTypeDescription
USERchar(32)User for which summary is generated.
HOSTchar(60)Host for which summary is generated.
EVENT_NAMEvarchar(128)Event name for which summary is generated.
COUNT_STARbigint(20) unsignedThe number of summarized events. This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedThe total wait time of the summarized timed events. This value is calculated only for timed events because nontimed events have a wait time of NULL. The same is true for the other xxx_TIMER_WAIT values.
MIN_TIMER_WAITbigint(20) unsignedThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedThe maximum wait time of the summarized timed events.
COUNT_READ_WRITEbigint(20) unsignedThe total number of only READ/WRITE transaction events.
SUM_TIMER_READ_WRITEbigint(20) unsignedThe total wait time of only READ/WRITE transaction events.
MIN_TIMER_READ_WRITEbigint(20) unsignedThe minimum wait time of only READ/WRITE transaction events.
AVG_TIMER_READ_WRITEbigint(20) unsignedThe average wait time of only READ/WRITE transaction events.
MAX_TIMER_READ_WRITEbigint(20) unsignedThe maximum wait time of only READ/WRITE transaction events.
COUNT_READ_ONLYbigint(20) unsignedThe total number of only READ ONLY transaction events.
SUM_TIMER_READ_ONLYbigint(20) unsignedThe total wait time of only READ ONLY transaction events.
MIN_TIMER_READ_ONLYbigint(20) unsignedThe minimum wait time of only READ ONLY transaction events.
AVG_TIMER_READ_ONLYbigint(20) unsignedThe average wait time of only READ ONLY transaction events.
MAX_TIMER_READ_ONLYbigint(20) unsignedThe maximum wait time of only READ ONLY transaction events.

1.1.2.9.2.1.25 Performance Schema events_transactions_summary_by_host_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_host_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_host_by_event_name table contains information on transaction events aggregated by host and event name.

The table contains the following columns:

ColumnTypeDescription
HOSTchar(60)Host for which summary is generated.
EVENT_NAMEvarchar(128)Event name for which summary is generated.
COUNT_STARbigint(20) unsignedThe number of summarized events. This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedThe total wait time of the summarized timed events. This value is calculated only for timed events because nontimed events have a wait time of NULL. The same is true for the other xxx_TIMER_WAIT values.
MIN_TIMER_WAITbigint(20) unsignedThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedThe maximum wait time of the summarized timed events.
COUNT_READ_WRITEbigint(20) unsignedThe total number of only READ/WRITE transaction events.
SUM_TIMER_READ_WRITEbigint(20) unsignedThe total wait time of only READ/WRITE transaction events.
MIN_TIMER_READ_WRITEbigint(20) unsignedThe minimum wait time of only READ/WRITE transaction events.
AVG_TIMER_READ_WRITEbigint(20) unsignedThe average wait time of only READ/WRITE transaction events.
MAX_TIMER_READ_WRITEbigint(20) unsignedThe maximum wait time of only READ/WRITE transaction events.
COUNT_READ_ONLYbigint(20) unsignedThe total number of only READ ONLY transaction events.
SUM_TIMER_READ_ONLYbigint(20) unsignedThe total wait time of only READ ONLY transaction events.
MIN_TIMER_READ_ONLYbigint(20) unsignedThe minimum wait time of only READ ONLY transaction events.
AVG_TIMER_READ_ONLYbigint(20) unsignedThe average wait time of only READ ONLY transaction events.
MAX_TIMER_READ_ONLYbigint(20) unsignedThe maximum wait time of only READ ONLY transaction events.

1.1.2.9.2.1.26 Performance Schema events_transactions_summary_by_thread_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_thread_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_thread_by_event_name table contains information on transaction events aggregated by thread and event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| THREAD_ID            | bigint(20) unsigned | NO   |     | NULL    |       |
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.2.9.2.1.27 Performance Schema events_transactions_summary_by_user_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_user_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_user_by_event_name table contains information on transaction events aggregated by user and event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| USER                 | char(32)            | YES  |     | NULL    |       |
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.2.9.2.1.28 Performance Schema events_transactions_summary_global_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_global_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_global_by_event_name table contains information on transaction events aggregated by event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.2.9.2.1.29 Performance Schema events_waits_current Table

The events_waits_current table contains the status of a thread's most recently monitored wait event, listing one event per thread.

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if the event has not ended or timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if the event has not ended or timing is not collected.
SPINSNumber of spin rounds for a mutex, or NULL if spin rounds are not used, or spinning is not instrumented.
OBJECT_SCHEMAName of the schema that contains the table for table I/O objects, otherwise NULL for file I/O and synchronization objects.
OBJECT_NAMEFile name for file I/O objects, table name for table I/O objects, the socket's IP:PORT value for a socket object or NULL for a synchronization object.
INDEX NAMEName of the index, PRIMARY for the primary key, or NULL for no index used.
OBJECT_TYPEFILE for a file object, TABLE or TEMPORARY TABLE for a table object, or NULL for a synchronization object.
OBJECT_INSTANCE_BEGINAddress in memory of the object.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. Either statement, stage or wait.
OPERATIONOperation type, for example read, write or lock
NUMBER_OF_BYTESNumber of bytes that the operation read or wrote, or NULL for table I/O waits.
FLAGSReserved for use in the future.

It is possible to empty this table with a TRUNCATE TABLE statement.

The related tables, events_waits_history and events_waits_history_long derive their values from the current events.

1.1.2.9.2.1.30 Performance Schema events_waits_history Table

The events_waits_history table by default contains the ten most recent completed wait events per thread. This number can be adjusted by setting the performance_schema_events_waits_history_size system variable when the server starts up.

The table structure is identical to the events_waits_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
SPINSNumber of spin rounds for a mutex, or NULL if spin rounds are not used, or spinning is not instrumented.
OBJECT_SCHEMAName of the schema that contains the table for table I/O objects, otherwise NULL for file I/O and synchronization objects.
OBJECT_NAMEFile name for file I/O objects, table name for table I/O objects, the socket's IP:PORT value for a socket object or NULL for a synchronization object.
INDEX NAMEName of the index, PRIMARY for the primary key, or NULL for no index used.
OBJECT_TYPEFILE for a file object, TABLE or TEMPORARY TABLE for a table object, or NULL for a synchronization object.
OBJECT_INSTANCE_BEGINAddress in memory of the object.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. Either statement, stage or wait.
OPERATIONOperation type, for example read, write or lock
NUMBER_OF_BYTESNumber of bytes that the operation read or wrote, or NULL for table I/O waits.
FLAGSReserved for use in the future.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_waits_current and events_waits_history_long are related tables.

1.1.2.9.2.1.31 Performance Schema events_waits_summary_by_account_by_event_name Table

The Performance Schema events_waits_summary_by_account_by_event_name table contains wait events summarized by account and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_account_by_event_name\G
...
*************************** 915. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 916. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 917. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 918. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.32 Performance Schema events_waits_summary_by_host_by_event_name Table

The Performance Schema events_waits_summary_by_host_by_event_name table contains wait events summarized by host and event name. It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_host_by_event_name\G
...
*************************** 610. row ***************************
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 611. row ***************************
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 612. row ***************************
          HOST: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.33 Performance Schema events_waits_summary_by_instance Table

The Performance Schema events_waits_summary_by_instance table contains wait events summarized by instance. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name. Used together with OBJECT_INSTANCE_BEGIN for grouping events.
OBJECT_INSTANCE_BEGINIf an instrument creates multiple instances, each instance has a unique OBJECT_INSTANCE_BEGIN value to allow for grouping by instance.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_instance\G
...
*************************** 202. row ***************************
           EVENT_NAME: wait/io/file/sql/binlog
OBJECT_INSTANCE_BEGIN: 140578961969856
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 90478331960
       MIN_TIMER_WAIT: 263344
       AVG_TIMER_WAIT: 15079721848
       MAX_TIMER_WAIT: 67760576376
*************************** 203. row ***************************
           EVENT_NAME: wait/io/file/sql/dbopt
OBJECT_INSTANCE_BEGIN: 140578961970560
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 39891428472
       MIN_TIMER_WAIT: 387168
       AVG_TIMER_WAIT: 6648571412
       MAX_TIMER_WAIT: 24503293304
*************************** 204. row ***************************
           EVENT_NAME: wait/io/file/sql/dbopt
OBJECT_INSTANCE_BEGIN: 140578961971264
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 39902495024
       MIN_TIMER_WAIT: 177888
       AVG_TIMER_WAIT: 6650415692
       MAX_TIMER_WAIT: 21026400404

1.1.2.9.2.1.34 Performance Schema events_waits_summary_by_thread_by_event_name Table

The Performance Schema events_waits_summary_by_thread_by_event_name table contains wait events summarized by thread and event name. It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_thread_by_event_name\G
...
*************************** 6424. row ***************************
     THREAD_ID: 64
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 6425. row ***************************
     THREAD_ID: 64
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 6426. row ***************************
     THREAD_ID: 64
    EVENT_NAME: idle
    COUNT_STAR: 73
SUM_TIMER_WAIT: 22005252162000000
MIN_TIMER_WAIT: 3000000
AVG_TIMER_WAIT: 301441810000000
MAX_TIMER_WAIT: 4912417573000000

1.1.2.9.2.1.35 Performance Schema events_waits_summary_by_user_by_event_name Table

The Performance Schema events_waits_summary_by_user_by_event_name table contains wait events summarized by user and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_user_by_event_name\G
...
*************************** 916. row ***************************
          USER: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 917. row ***************************
          USER: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 918. row ***************************
          USER: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.2.9.2.1.36 Performance Schema events_waits_summary_global_by_event_name Table

The Performance Schema events_waits_summary_global_by_event_name table contains wait events summarized by event name. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_global_by_event_name\G
...
*************************** 303. row ***************************
    EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 304. row ***************************
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 305. row ***************************
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 306. row ***************************
    EVENT_NAME: idle
    COUNT_STAR: 265
SUM_TIMER_WAIT: 46861125181000000
MIN_TIMER_WAIT: 1000000
AVG_TIMER_WAIT: 176834434000000
MAX_TIMER_WAIT: 4912417573000000

1.1.2.9.2.1.37 Performance Schema file_instances Table

Description

The file_instances table lists instances of instruments seen by the Performance Schema when executing file I/O instrumentation, and the associated files. Only files that have been opened, and that have not been deleted, will be listed in the table.

The performance_schema_max_file_instances system variable specifies the maximum number of instrumented file objects.

ColumnDescription
FILE_NAMEFile name.
EVENT_NAMEInstrument name associated with the file.
OPEN_COUNTOpen handles on the file. A value of greater than zero means that the file is currently open.

Example

SELECT * FROM performance_schema.file_instances WHERE OPEN_COUNT>0;
+----------------------------------------------------+--------------------------------------+------------+
| FILE_NAME                                          | EVENT_NAME                           | OPEN_COUNT |
+----------------------------------------------------+--------------------------------------+------------+
| /var/log/mysql/mariadb-bin.index                   | wait/io/file/sql/binlog_index        |          1 |
| /var/lib/mysql/ibdata1                             | wait/io/file/innodb/innodb_data_file |          2 |
| /var/lib/mysql/ib_logfile0                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/ib_logfile1                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/mysql/gtid_slave_pos.ibd            | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_index_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_table_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
...

1.1.2.9.2.1.38 Performance Schema file_summary_by_event_name Table

The Performance Schema file_summary_by_event_name table contains file events summarized by event name. As of MariaDB 10.0, it contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including FGETS, FGETC, FREAD, and READ.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including FPUTS, FPUTC, FPRINTF, VFPRINTF, FWRITE, and PWRITE.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CREATE, DELETE, OPEN, CLOSE, STREAM_OPEN, STREAM_CLOSE, SEEK, TELL, FLUSH, STAT, FSTAT, CHSIZE, RENAME, and SYNC.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

Before MariaDB 10, the table contained only the EVENT_NAME, COUNT_READ, COUNT_WRITE, SUM_NUMBER_OF_BYTES_READ and SUM_NUMBER_OF_BYTES_WRITE columns.

I/O operations can be avoided by caching, in which case they will not be recorded in this table.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM file_summary_by_event_name\G
...
*************************** 49. row ***************************
               EVENT_NAME: wait/io/file/aria/MAD
               COUNT_STAR: 60
           SUM_TIMER_WAIT: 397234368
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 6620224
           MAX_TIMER_WAIT: 16808672
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 60
           SUM_TIMER_MISC: 397234368
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 6620224
           MAX_TIMER_MISC: 16808672
*************************** 50. row ***************************
               EVENT_NAME: wait/io/file/aria/control
               COUNT_STAR: 3
           SUM_TIMER_WAIT: 24055778544
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 8018592848
           MAX_TIMER_WAIT: 24027262400
               COUNT_READ: 1
           SUM_TIMER_READ: 24027262400
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 24027262400
           MAX_TIMER_READ: 24027262400
 SUM_NUMBER_OF_BYTES_READ: 52
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 2
           SUM_TIMER_MISC: 28516144
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 14258072
           MAX_TIMER_MISC: 27262208

1.1.2.9.2.1.39 Performance Schema file_summary_by_instance Table

The Performance Schema file_summary_by_instance table contains file events summarized by instance. As of MariaDB 10.0, it contains the following columns:

ColumnDescription
FILE_NAMEFile name.
EVENT_NAMEEvent name.
OBJECT_INSTANCE_BEGINAddress in memory. Together with FILE_NAME and EVENT_NAME uniquely identifies a row.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including FGETS, FGETC, FREAD, and READ.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including FPUTS, FPUTC, FPRINTF, VFPRINTF, FWRITE, and PWRITE.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CREATE, DELETE, OPEN, CLOSE, STREAM_OPEN, STREAM_CLOSE, SEEK, TELL, FLUSH, STAT, FSTAT, CHSIZE, RENAME, and SYNC.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

Before MariaDB 10, the table contained only the FILE_NAME, EVENT_NAME, COUNT_READ, COUNT_WRITE, SUM_NUMBER_OF_BYTES_READ and SUM_NUMBER_OF_BYTES_WRITE columns.

I/O operations can be avoided by caching, in which case they will not be recorded in this table.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM file_summary_by_instance\G
...
*************************** 204. row ***************************
                FILE_NAME: /var/lib/mysql/test/db.opt
               EVENT_NAME: wait/io/file/sql/dbopt
    OBJECT_INSTANCE_BEGIN: 140578961971264
               COUNT_STAR: 6
           SUM_TIMER_WAIT: 39902495024
           MIN_TIMER_WAIT: 177888
           AVG_TIMER_WAIT: 6650415692
           MAX_TIMER_WAIT: 21026400404
               COUNT_READ: 1
           SUM_TIMER_READ: 21026400404
           MIN_TIMER_READ: 21026400404
           AVG_TIMER_READ: 21026400404
           MAX_TIMER_READ: 21026400404
 SUM_NUMBER_OF_BYTES_READ: 65
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 5
           SUM_TIMER_MISC: 18876094620
           MIN_TIMER_MISC: 177888
           AVG_TIMER_MISC: 3775218924
           MAX_TIMER_MISC: 18864558060
*************************** 205. row ***************************
                FILE_NAME: /var/log/mysql/mariadb-bin.000157
               EVENT_NAME: wait/io/file/sql/binlog
    OBJECT_INSTANCE_BEGIN: 140578961971968
               COUNT_STAR: 6
           SUM_TIMER_WAIT: 73985877680
           MIN_TIMER_WAIT: 251136
           AVG_TIMER_WAIT: 12330979468
           MAX_TIMER_WAIT: 73846656340
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 2
          SUM_TIMER_WRITE: 62583004
          MIN_TIMER_WRITE: 27630192
          AVG_TIMER_WRITE: 31291284
          MAX_TIMER_WRITE: 34952812
SUM_NUMBER_OF_BYTES_WRITE: 369
               COUNT_MISC: 4
           SUM_TIMER_MISC: 73923294676
           MIN_TIMER_MISC: 251136
           AVG_TIMER_MISC: 18480823560
           MAX_TIMER_MISC: 73846656340

1.1.2.9.2.1.40 Performance Schema global_status Table

MariaDB starting with 10.5.2

The global_status table was added in MariaDB 10.5.2.

The global_status table contains a list of status variables and their global values. The table only stores status variable statistics for threads which are instrumented, and does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEThe global status variable name.
VARIABLE_VALUEThe global status variable value.

TRUNCATE TABLE resets global status variables, including thread, account, host, and user status, but not those that are never reset by the server.

1.1.2.9.2.1.41 Performance Schema hosts Table

Description

The hosts table contains a row for each host used by clients to connect to the server, containing current and total connections.

The size is determined by the performance_schema_hosts_size system variable, which, if set to zero, will disable connection statistics in the hosts table.

It contains the following columns:

ColumnDescription
HOSTHost name used by the client to connect, NULL for internal threads or user sessions that failed to authenticate.
CURRENT_CONNECTIONSCurrent number of the host's connections.
TOTAL_CONNECTIONSTotal number of the host's connections

Example

SELECT * FROM hosts;
+-----------+---------------------+-------------------+
| HOST      | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+-----------+---------------------+-------------------+
| localhost |                   1 |                45 |
| NULL      |                  20 |                23 |
+-----------+---------------------+-------------------+

1.1.2.9.2.1.42 Performance Schema memory_summary_by_account_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_account_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_account_by_event_name table contains memory usage statistics aggregated by account and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
USERchar(32)YESNULLUser portion of the account.
HOSTchar(60)YESNULLHost portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.2.9.2.1.43 Performance Schema memory_summary_by_host_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_host_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_host_by_event_name table contains memory usage statistics aggregated by host and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
HOSTchar(60)YESNULLHost portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.2.9.2.1.44 Performance Schema memory_summary_by_thread_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_thread_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_thread_by_event_name table contains memory usage statistics aggregated by thread and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
THREAD_IDbigint(20) unsignedNONULLThread id.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.2.9.2.1.45 Performance Schema memory_summary_by_user_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_user_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_user_by_event_name table contains memory usage statistics aggregated by user and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
USERchar(32)YESNULLUser portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.2.9.2.1.46 Performance Schema memory_summary_global_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_global_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_global_by_event_name table contains memory usage statistics aggregated by event and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

Example

Seeing what memory was most often allocated for:

SELECT * FROM memory_summary_global_by_event_name 
  ORDER BY count_alloc DESC LIMIT 1\G
*************************** 1. row ***************************
                  EVENT_NAME: memory/sql/QUICK_RANGE_SELECT::alloc
                 COUNT_ALLOC: 147976
                  COUNT_FREE: 147976
   SUM_NUMBER_OF_BYTES_ALLOC: 600190656
    SUM_NUMBER_OF_BYTES_FREE: 600190656
              LOW_COUNT_USED: 0
          CURRENT_COUNT_USED: 0
             HIGH_COUNT_USED: 68
    LOW_NUMBER_OF_BYTES_USED: 0
CURRENT_NUMBER_OF_BYTES_USED: 0
   HIGH_NUMBER_OF_BYTES_USED: 275808

1.1.2.9.2.1.47 Performance Schema metadata_locks Table

MariaDB starting with 10.5.2

The metadata_locks table was introduced in MariaDB 10.5.2.

The metadata_locks table contains metadata lock information.

To enable metadata lock instrumention, at runtime:

UPDATE performance_schema.setup_instruments SET enabled='YES', timed='YES' 
  WHERE name LIKE 'wait/lock/metadata%';

or in the configuration file:

performance-schema-instrument='wait/lock/metadata/sql/mdl=ON'

The table is by default autosized, but the size can be configured with the performance_schema_max_metadata_locks system variabe.

The table is read-only, and TRUNCATE TABLE cannot be used to empty the table.

The table contains the following columns:

FieldTypeNullDefaultDescription
OBJECT_TYPEvarchar(64)NONULLObject type. One of BACKUP, COMMIT, EVENT, FUNCTION, GLOBAL, LOCKING SERVICE, PROCEDURE, SCHEMA, TABLE, TABLESPACE, TRIGGER (unused) or USER LEVEL LOCK.
OBJECT_SCHEMAvarchar(64)YESNULLObject schema.
OBJECT_NAMEvarchar(64)YESNULLObject name.
OBJECT_INSTANCE_BEGINbigint(20) unsignedNONULLAddress in memory of the instrumented object.
LOCK_TYPEvarchar(32)NONULLLock type. One of BACKUP_FTWRL1, BACKUP_START, BACKUP_TRANS_DML, EXCLUSIVE, INTENTION_EXCLUSIVE, SHARED, SHARED_HIGH_PRIO, SHARED_NO_READ_WRITE, SHARED_NO_WRITE, SHARED_READ, SHARED_UPGRADABLE or SHARED_WRITE.
LOCK_DURATIONvarchar(32)NONULLLock duration. One of EXPLICIT (locks released by explicit action, for example a global lock acquired with FLUSH TABLES WITH READ LOCK) , STATEMENT (locks implicitly released at statement end) or TRANSACTION (locks implicitly released at transaction end).
LOCK_STATUSvarchar(32)NONULLLock status. One of GRANTED, KILLED, PENDING, POST_RELEASE_NOTIFY, PRE_ACQUIRE_NOTIFY, TIMEOUT or VICTIM.
SOURCEvarchar(64)YESNULLSource file containing the instrumented code that produced the event, as well as the line number where the instrumentation occurred. This allows one to examine the source code involved.
OWNER_THREAD_IDbigint(20) unsignedYESNULLThread that requested the lock.
OWNER_EVENT_IDbigint(20) unsignedYESNULLEvent that requested the lock.

1.1.2.9.2.1.48 Performance Schema mutex_instances Table

Description

The mutex_instances table lists all mutexes that the Performance Schema seeing while the server is executing.

A mutex is a code mechanism for ensuring that threads can only access resources one at a time. A second thread attempting to access a resource will find it protected by a mutex, and will wait for it to be unlocked.

The performance_schema_max_mutex_instances system variable specifies the maximum number of instrumented mutex instances.

ColumnDescription
NAMEInstrument name associated with the mutex.
OBJECT_INSTANCE_BEGINMemory address of the instrumented mutex.
LOCKED_BY_THREAD_IDThe THREAD_ID of the locking thread if a thread has a mutex locked, otherwise NULL.

1.1.2.9.2.1.49 Performance Schema objects_summary_global_by_type Table

It aggregates object wait events, and contains the following columns:

ColumnDescription
OBJECT_TYPEGroups records together with OBJECT_SCHEMA and OBJECT_NAME.
OBJECT_SCHEMAGroups records together with OBJECT_TYPE and OBJECT_NAME.
OBJECT_NAMEGroups records together with OBJECT_SCHEMA and OBJECT_TYPE.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM objects_summary_global_by_type\G
...
*************************** 101. row ***************************
   OBJECT_TYPE: TABLE
 OBJECT_SCHEMA: test
   OBJECT_NAME: v
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 102. row ***************************
   OBJECT_TYPE: TABLE
 OBJECT_SCHEMA: test
   OBJECT_NAME: xx2
    COUNT_STAR: 2
SUM_TIMER_WAIT: 1621920
MIN_TIMER_WAIT: 481344
AVG_TIMER_WAIT: 810960
MAX_TIMER_WAIT: 1140576

1.1.2.9.2.1.50 Performance Schema performance_timers Table

Description

The performance_timers table lists available event timers.

It contains the following columns:

ColumnDescription
TIMER_NAMETime name, used in the setup_timers table.
TIMER_FREQUENCYNumber of timer units per second. Dependent on the processor speed.
TIMER_RESOLUTIONNumber of timer units by which timed values increase each time.
TIMER_OVERHEADMinimum timer overhead, determined during initialization by calling the timer 20 times and selecting the smallest value. Total overhead will be at least double this, as the timer is called at the beginning and end of each timed event.

Any NULL values indicate that that particular timer is not available on your platform, Any timer names with a non-NULL value can be used in the setup_timers table.

Example

SELECT * FROM performance_timers;
+-------------+-----------------+------------------+---------------------+
| TIMER_NAME  | TIMER_FREQUENCY | TIMER_RESOLUTION | TIMER_OVERHEAD      |
+-------------+-----------------+------------------+---------------------+
| CYCLE       |      2293651741 |                1 |                  28 |
| NANOSECOND  |      1000000000 |                1 |                  48 |
| MICROSECOND |         1000000 |                1 |                  52 |
| MILLISECOND |            1000 |             1000 | 9223372036854775807 |
| TICK        |             106 |                1 |                 496 |
+-------------+-----------------+------------------+---------------------+

1.1.2.9.2.1.51 Performance Schema prepared_statements_instances Table

MariaDB starting with 10.5.2

The prepared_statements_instances table was introduced in MariaDB 10.5.2.

The prepared_statements_instances table contains aggregated statistics of prepared statements.

The maximum number of rows in the table is determined by the performance_schema_max_prepared_statement_instances system variable, which is by default autosized on startup.

The table contains the following columns:

+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+
| Field                       | Type                                                   | Null | Key | Default | Extra |
+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+
| OBJECT_INSTANCE_BEGIN       | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| STATEMENT_ID                | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| STATEMENT_NAME              | varchar(64)                                            | YES  |     | NULL    |       |
| SQL_TEXT                    | longtext                                               | NO   |     | NULL    |       |
| OWNER_THREAD_ID             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| OWNER_EVENT_ID              | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| OWNER_OBJECT_TYPE           | enum('EVENT','FUNCTION','PROCEDURE','TABLE','TRIGGER') | YES  |     | NULL    |       |
| OWNER_OBJECT_SCHEMA         | varchar(64)                                            | YES  |     | NULL    |       |
| OWNER_OBJECT_NAME           | varchar(64)                                            | YES  |     | NULL    |       |
| TIMER_PREPARE               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| COUNT_REPREPARE             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| COUNT_EXECUTE               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| MIN_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| AVG_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| MAX_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_LOCK_TIME               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ERRORS                  | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_WARNINGS                | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_AFFECTED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_SENT               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_EXAMINED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_CREATED_TMP_DISK_TABLES | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_CREATED_TMP_TABLES      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_FULL_JOIN        | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_FULL_RANGE_JOIN  | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_RANGE            | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_RANGE_CHECK      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_SCAN             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_MERGE_PASSES       | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_RANGE              | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_ROWS               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_SCAN               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_NO_INDEX_USED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_NO_GOOD_INDEX_USED      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+

1.1.2.9.2.1.52 Performance Schema replication_applier_configuration Table

MariaDB starting with 10.5.2

The replication_applier_configuration table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

The Performance Schema replication_applier_configuration table contains configuration settings affecting replica transactions.

It contains the following fields.

FieldTypeNullDescription
CHANNEL_NAMEchar(64)NOReplication channel name.
DESIRED_DELAYint(11)NOTarget number of seconds the replica should be delayed to the master.

1.1.2.9.2.1.53 Performance Schema replication_applier_status Table

MariaDB starting with 10.5.2

The replication_applier_status table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

The Performance Schema replication_applier_status table contains information about the general transaction execution status on the replica.

It contains the following fields.

FieldTypeNullDescription
CHANNEL_NAMEchar(64)NOThe replication channel name.
SERVICE_STATEenum('ON','OFF')NOShows ON when the replication channel's applier threads are active or idle, OFF means that the applier threads are not active.
REMAINING_DELAYint(10) unsignedYESSeconds the replica needs to wait to reach the desired delay from master.
COUNT_TRANSACTIONS_RETRIESbigint(20) unsignedNOThe number of retries that were made because the replication SQL thread failed to apply a transaction.

1.1.2.9.2.1.54 Performance Schema replication_applier_status_by_coordinator Table

MariaDB starting with 10.5.2

The replication_applier_status_by_coordinator table was added in MariaDB 10.5.2.

The Performance Schema replication_applier_status_by_coordinator table displays the status of the coordinator thread used in multi-threaded replicas to manage multiple worker threads.

It contains the following fields.

ColumnTypeNullDescription
CHANNEL_NAMEvarchar(256)NOReplication channel name.
THREAD_IDbigint(20) unsignedYESThe SQL/coordinator thread ID.
SERVICE_STATEenum('ON','OFF')NOON (thread exists and is active or idle) or OFF (thread no longer exists).
LAST_ERROR_NUMBERint(11)NOLast error number that caused the SQL/coordinator thread to stop.
LAST_ERROR_MESSAGEvarchar(1024)NOLast error message that caused the SQL/coordinator thread to stop.
LAST_ERROR_TIMESTAMPtimestampNOTimestamp that shows when the most recent SQL/coordinator error occured.
LAST_SEEN_TRANSACTIONchar(57)NOThe transaction the worker has last seen.
LAST_TRANS_RETRY_COUNTint(11)NOTotal number of retries attempted by last transaction.

1.1.2.9.2.1.55 Performance Schema replication_applier_status_by_worker Table

MariaDB starting with 10.6.0

The replication_applier_status_by_worker table was added in MariaDB 10.6.0.

The Performance Schema replication_applier_status_by_worker table displays replica worker thread specific information.

It contains the following fields.

ColumnDescription
CHANNEL_NAMEName of replication channel through which the transaction is received.
THREAD_IDThread_Id as displayed in the performance_schema.threads table for thread with name 'thread/sql/rpl_parallel_thread'. THREAD_ID will be NULL when worker threads are stopped due to error/force stop.
SERVICE_STATEWhether or not the thread is running.
LAST_SEEN_TRANSACTIONLast GTID executed by worker
LAST_ERROR_NUMBERLast Error that occurred on a particular worker.
LAST_ERROR_MESSAGELast error specific message.
LAST_ERROR_TIMESTAMPTime stamp of last error.
WORKER_IDLE_TIMETotal idle time in seconds that the worker thread has spent waiting for work from SQL thread.
LAST_TRANS_RETRY_COUNTTotal number of retries attempted by last transaction.

1.1.2.9.2.1.56 Performance Schema replication_connection_configuration Table

MariaDB starting with 10.5.2

The replication_connection_configuration table was added in MariaDB 10.6.0.

The Performance Schema replication_connection_configuration table displays replica's configuration settings used for connecting to the primary.

It contains the following fields.

ColumnTypeNullDescription
CHANNEL_NAMEvarchar(256)NOThe replication channel used.
HOSTchar(60)NOThe host name of the source that the replica is connected to.
PORTint(11)NOThe port used to connect to the source.
USERchar(32)NOThe user name of the replication user account used to connect to the source.
USING_GTIDenum('NO', 'CURRENT_POS', 'SLAVE_POS')NOWhether replication is using GTIDs or not.
SSL_ALLOWEDenum('YES', 'NO', 'IGNORED')NOWhether SSL is allowed for the replica connection.
SSL_CA_FILEvarchar(512)NOPath to the file that contains one or more certificates for trusted Certificate Authorities (CA) to use for TLS.
SSL_CA_PATHvarchar(512)NOPath to a directory that contains one or more PEM files that contain X509 certificates for a trusted Certificate Authority (CA) to use for TLS.
SSL_CERTIFICATEvarchar(512)NOPath to the certificate used to authenticate the master.
SSL_CIPHERvarchar(512)NOWhich cipher is used for encription.
SSL_KEYvarchar(512)NOPath to the private key used for TLS.
SSL_VERIFY_SERVER_CERTIFICATEenum('YES','NO')NOWhether the server certificate is verified as part of the SSL connection.
SSL_CRL_FILEvarchar(255)NOPath to the PEM file containing one or more revoked X.509 certificates.
SSL_CRL_PATHvarchar(255)NOPATH to a folder containing PEM files containing one or more revoked X.509 certificates.
CONNECTION_RETRY_INTERVALint(11)NOThe number of seconds between connect retries.
CONNECTION_RETRY_COUNTbigint(20) unsignedNOThe number of times the replica can attempt to reconnect to the source in the event of a lost connection.
HEARTBEAT_INTERVALdouble(10,3) unsignedNONumber of seconds after which a heartbeat will be sent.
IGNORE_SERVER_IDSlongtextNOBinary log events from servers (ids) to ignore.
REPL_DO_DOMAIN_IDSlongtextNOOnly apply binary logs from these domain ids.
REPL_IGNORE_DOMAIN_IDSlongtextNOBinary log events from domains to ignore.

1.1.2.9.2.1.57 Performance Schema rwlock_instances Table

The rwlock_instances table lists all read write lock (rwlock) instances that the Performance Schema sees while the server is executing. A read write is a mechanism for ensuring threads can either share access to common resources, or have exclusive access.

The performance_schema_max_rwlock_instances system variable specifies the maximum number of instrumented rwlock objects.

The rwlock_instances table contains the following columns:

ColumnDescription
NAMEInstrument name associated with the read write lock
OBJECT_INSTANCE_BEGINAddress in memory of the instrumented lock
WRITE_LOCKED_BY_THREAD_IDTHREAD_ID of the locking thread if locked in write (exclusive) mode, otherwise NULL.
READ_LOCKED_BY_COUNTCount of current read locks held

1.1.2.9.2.1.58 Performance Schema session_account_connect_attrs Table

Description

The session_account_connect_attrs table shows connection attributes for the current session.

Applications can pass key/value connection attributes to the server when a connection is made. The session_connect_attrs and session_account_connect_attrs tables provide access to this information, for all sessions and the current session respectively.

The C API functions mysql_options() and mysql_optionsv() are used for passing connection attributes to the server.

session_account_connect_attrs contains the following columns:

ColumnDescription
PROCESSLIST_IDSession connection identifier.
ATTR_NAMEAttribute name.
ATTR_VALUEAttribute value.
ORDINAL_POSITIONOrder in which attribute was added to the connection attributes.

Example

SELECT * FROM performance_schema.session_account_connect_attrs;
+----------------+-----------------+------------------+------------------+
| PROCESSLIST_ID | ATTR_NAME       | ATTR_VALUE       | ORDINAL_POSITION |
+----------------+-----------------+------------------+------------------+
|             45 | _os             | debian-linux-gnu |                0 |
|             45 | _client_name    | libmysql         |                1 |
|             45 | _pid            | 7711             |                2 |
|             45 | _client_version | 10.0.5           |                3 |
|             45 | _platform       | x86_64           |                4 |
|             45 | program_name    | mysql            |                5 |
+----------------+-----------------+------------------+------------------+

1.1.2.9.2.1.59 Performance Schema session_connect_attrs Table

Description

The session_connect_attrs table shows connection attributes for all sessions.

Applications can pass key/value connection attributes to the server when a connection is made. The session_connect_attrs and session_account_connect_attrs tables provide access to this information, for all sessions and the current session respectively.

The C API functions mysql_options() and mysql_optionsv() are used for passing connection attributes to the server.

session_connect_attrs contains the following columns:

ColumnDescription
PROCESSLIST_IDSession connection identifier.
ATTR_NAMEAttribute name.
ATTR_VALUEAttribute value.
ORDINAL_POSITIONOrder in which attribute was added to the connection attributes.

Example

Returning the current connection's attributes:

SELECT * FROM performance_schema.session_connect_attrs WHERE processlist_id=CONNECTION_ID();
+----------------+-----------------+------------------+------------------+
| PROCESSLIST_ID | ATTR_NAME       | ATTR_VALUE       | ORDINAL_POSITION |
+----------------+-----------------+------------------+------------------+
|             45 | _os             | debian-linux-gnu |                0 |
|             45 | _client_name    | libmysql         |                1 |
|             45 | _pid            | 7711             |                2 |
|             45 | _client_version | 10.0.5           |                3 |
|             45 | _platform       | x86_64           |                4 |
|             45 | program_name    | mysql            |                5 |
+----------------+-----------------+------------------+------------------+

1.1.2.9.2.1.60 Performance Schema session_status Table

MariaDB starting with 10.5.2

The session_status table was added in MariaDB 10.5.2.

The session_status table contains a list of status variables for the current session. The table only stores status variable statistics for threads which are instrumented, and does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEThe session status variable name.
VARIABLE_VALUEThe session status variable value.

It is not possible to empty this table with a TRUNCATE TABLE statement.

1.1.2.9.2.1.61 Performance Schema setup_actors Table

The setup_actors table contains information for determining whether monitoring should be enabled for new client connection threads.

The default size is 100 rows, which can be changed by modifying the performance_schema_setup_actors_size system variable at server startup.

If a row in the table matches a new foreground thread's client and host, the matching INSTRUMENTED column in the threads table is set to either YES or NO, which allows selective application of instrumenting by host, by user, or combination thereof.

ColumnDescription
HOSTHost name, either a literal, or the % wildcard representing any host.
USERUser name, either a literal or the % wildcard representing any name.
ROLEUnused

Initially, any user and host is matched:

SELECT * FROM performance_schema.setup_actors;
+------+------+------+
| HOST | USER | ROLE |
+------+------+------+
| %    | %    | %    |
+------+------+------+

1.1.2.9.2.1.62 Performance Schema setup_consumers Table

Lists the types of consumers for which event information is available.

The setup_consumers table contains the following columns:

ColumnDescription
NAMEConsumer name
ENABLEDYES or NO for whether or not the consumer is enabled. You can modify this column to ensure that event information is added, or is not added.

The table can be modified directly, or the server started with the option enabled, for example:

performance-schema-consumer-events-waits-history=ON

Example

SELECT * FROM performance_schema.setup_consumers;

+--------------------------------+---------+
| NAME                           | ENABLED |
+--------------------------------+---------+
| events_stages_current          | NO      |
| events_stages_history          | NO      |
| events_stages_history_long     | NO      |
| events_statements_current      | YES     |
| events_statements_history      | NO      |
| events_statements_history_long | NO      |
| events_waits_current           | NO      |
| events_waits_history           | NO      |
| events_waits_history_long      | NO      |
| global_instrumentation         | YES     |
| thread_instrumentation         | YES     |
| statements_digest              | YES     |
+--------------------------------+---------+

1.1.2.9.2.1.63 Performance Schema setup_instruments Table

The setup_instruments table contains a list of instrumented object classes for which it is possible to collect events. There is one row for each instrument in the source code. When an instrument is enabled and executed, instances are created which are then stored in the cond_instances, file_instances, mutex_instances, rwlock_instances or socket_instance tables.

It contains the following columns:

ColumnDescription
NAMEInstrument name
ENABLEDWhether or not the instrument is enabled. It can be disabled, and the instrument will produce no events.
TIMEDWhether or not the instrument is timed. It can be set, but if disabled, events produced by the instrument will have NULL values for the corresponding TIMER_START, TIMER_END, and TIMER_WAIT values.

Example

From MariaDB 10.5.7, default settings with the Performance Schema enabled:

SELECT * FROM setup_instruments ORDER BY name;
+--------------------------------------------------------------------------------+---------+-------+
| NAME                                                                           | ENABLED | TIMED |
+--------------------------------------------------------------------------------+---------+-------+
| idle                                                                           | YES     | YES   |
| memory/csv/blobroot                                                            | NO      | NO    |
| memory/csv/row                                                                 | NO      | NO    |
| memory/csv/tina_set                                                            | NO      | NO    |
| memory/csv/TINA_SHARE                                                          | NO      | NO    |
| memory/csv/Transparent_file                                                    | NO      | NO    |
| memory/innodb/adaptive hash index                                              | NO      | NO    |
| memory/innodb/btr0btr                                                          | NO      | NO    |
| memory/innodb/btr0buf                                                          | NO      | NO    |
| memory/innodb/btr0bulk                                                         | NO      | NO    |
| memory/innodb/btr0cur                                                          | NO      | NO    |
| memory/innodb/btr0pcur                                                         | NO      | NO    |
| memory/innodb/btr0sea                                                          | NO      | NO    |
| memory/innodb/buf0buf                                                          | NO      | NO    |
| memory/innodb/buf0dblwr                                                        | NO      | NO    |
| memory/innodb/buf0dump                                                         | NO      | NO    |
| memory/innodb/buf_buf_pool                                                     | NO      | NO    |
| memory/innodb/dict0dict                                                        | NO      | NO    |
| memory/innodb/dict0mem                                                         | NO      | NO    |
| memory/innodb/dict0stats                                                       | NO      | NO    |
| memory/innodb/dict_stats_bg_recalc_pool_t                                      | NO      | NO    |
| memory/innodb/dict_stats_index_map_t                                           | NO      | NO    |
| memory/innodb/dict_stats_n_diff_on_level                                       | NO      | NO    |
| memory/innodb/eval0eval                                                        | NO      | NO    |
| memory/innodb/fil0crypt                                                        | NO      | NO    |
| memory/innodb/fil0fil                                                          | NO      | NO    |
| memory/innodb/fsp0file                                                         | NO      | NO    |
| memory/innodb/fts0ast                                                          | NO      | NO    |
| memory/innodb/fts0blex                                                         | NO      | NO    |
| memory/innodb/fts0config                                                       | NO      | NO    |
| memory/innodb/fts0file                                                         | NO      | NO    |
| memory/innodb/fts0fts                                                          | NO      | NO    |
| memory/innodb/fts0opt                                                          | NO      | NO    |
| memory/innodb/fts0pars                                                         | NO      | NO    |
| memory/innodb/fts0que                                                          | NO      | NO    |
| memory/innodb/fts0sql                                                          | NO      | NO    |
| memory/innodb/fts0tlex                                                         | NO      | NO    |
| memory/innodb/gis0sea                                                          | NO      | NO    |
| memory/innodb/handler0alter                                                    | NO      | NO    |
| memory/innodb/hash0hash                                                        | NO      | NO    |
| memory/innodb/ha_innodb                                                        | NO      | NO    |
| memory/innodb/i_s                                                              | NO      | NO    |
| memory/innodb/lexyy                                                            | NO      | NO    |
| memory/innodb/lock0lock                                                        | NO      | NO    |
| memory/innodb/mem0mem                                                          | NO      | NO    |
| memory/innodb/os0event                                                         | NO      | NO    |
| memory/innodb/os0file                                                          | NO      | NO    |
| memory/innodb/other                                                            | NO      | NO    |
| memory/innodb/pars0lex                                                         | NO      | NO    |
| memory/innodb/rem0rec                                                          | NO      | NO    |
| memory/innodb/row0ftsort                                                       | NO      | NO    |
| memory/innodb/row0import                                                       | NO      | NO    |
| memory/innodb/row0log                                                          | NO      | NO    |
| memory/innodb/row0merge                                                        | NO      | NO    |
| memory/innodb/row0mysql                                                        | NO      | NO    |
| memory/innodb/row0sel                                                          | NO      | NO    |
| memory/innodb/row_log_buf                                                      | NO      | NO    |
| memory/innodb/row_merge_sort                                                   | NO      | NO    |
| memory/innodb/srv0start                                                        | NO      | NO    |
| memory/innodb/std                                                              | NO      | NO    |
| memory/innodb/sync0arr                                                         | NO      | NO    |
| memory/innodb/sync0debug                                                       | NO      | NO    |
| memory/innodb/sync0rw                                                          | NO      | NO    |
| memory/innodb/sync0start                                                       | NO      | NO    |
| memory/innodb/sync0types                                                       | NO      | NO    |
| memory/innodb/trx0i_s                                                          | NO      | NO    |
| memory/innodb/trx0roll                                                         | NO      | NO    |
| memory/innodb/trx0rseg                                                         | NO      | NO    |
| memory/innodb/trx0seg                                                          | NO      | NO    |
| memory/innodb/trx0trx                                                          | NO      | NO    |
| memory/innodb/trx0undo                                                         | NO      | NO    |
| memory/innodb/ut0list                                                          | NO      | NO    |
| memory/innodb/ut0mem                                                           | NO      | NO    |
| memory/innodb/ut0new                                                           | NO      | NO    |
| memory/innodb/ut0pool                                                          | NO      | NO    |
| memory/innodb/ut0rbt                                                           | NO      | NO    |
| memory/innodb/ut0wqueue                                                        | NO      | NO    |
| memory/innodb/xtrabackup                                                       | NO      | NO    |
| memory/memory/HP_INFO                                                          | NO      | NO    |
| memory/memory/HP_KEYDEF                                                        | NO      | NO    |
| memory/memory/HP_PTRS                                                          | NO      | NO    |
| memory/memory/HP_SHARE                                                         | NO      | NO    |
| memory/myisam/filecopy                                                         | NO      | NO    |
| memory/myisam/FTB                                                              | NO      | NO    |
| memory/myisam/FTPARSER_PARAM                                                   | NO      | NO    |
| memory/myisam/FT_INFO                                                          | NO      | NO    |
| memory/myisam/ft_memroot                                                       | NO      | NO    |
| memory/myisam/ft_stopwords                                                     | NO      | NO    |
| memory/myisam/keycache_thread_var                                              | NO      | NO    |
| memory/myisam/MI_DECODE_TREE                                                   | NO      | NO    |
| memory/myisam/MI_INFO                                                          | NO      | NO    |
| memory/myisam/MI_INFO::bulk_insert                                             | NO      | NO    |
| memory/myisam/MI_INFO::ft1_to_ft2                                              | NO      | NO    |
| memory/myisam/MI_SORT_PARAM                                                    | NO      | NO    |
| memory/myisam/MI_SORT_PARAM::wordroot                                          | NO      | NO    |
| memory/myisam/MYISAM_SHARE                                                     | NO      | NO    |
| memory/myisam/MYISAM_SHARE::decode_tables                                      | NO      | NO    |
| memory/myisam/preload_buffer                                                   | NO      | NO    |
| memory/myisam/record_buffer                                                    | NO      | NO    |
| memory/myisam/SORT_FT_BUF                                                      | NO      | NO    |
| memory/myisam/SORT_INFO::buffer                                                | NO      | NO    |
| memory/myisam/SORT_KEY_BLOCKS                                                  | NO      | NO    |
| memory/myisam/stPageList::pages                                                | NO      | NO    |
| memory/myisammrg/children                                                      | NO      | NO    |
| memory/myisammrg/MYRG_INFO                                                     | NO      | NO    |
| memory/partition/ha_partition::file                                            | NO      | NO    |
| memory/partition/ha_partition::part_ids                                        | NO      | NO    |
| memory/partition/Partition_admin                                               | NO      | NO    |
| memory/partition/Partition_share                                               | NO      | NO    |
| memory/partition/partition_sort_buffer                                         | NO      | NO    |
| memory/performance_schema/accounts                                             | YES     | NO    |
| memory/performance_schema/cond_class                                           | YES     | NO    |
| memory/performance_schema/cond_instances                                       | YES     | NO    |
| memory/performance_schema/events_stages_history                                | YES     | NO    |
| memory/performance_schema/events_stages_history_long                           | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_account_by_event_name       | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_host_by_event_name          | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_thread_by_event_name        | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_user_by_event_name          | YES     | NO    |
| memory/performance_schema/events_stages_summary_global_by_event_name           | YES     | NO    |
| memory/performance_schema/events_statements_current                            | YES     | NO    |
| memory/performance_schema/events_statements_current.sqltext                    | YES     | NO    |
| memory/performance_schema/events_statements_current.tokens                     | YES     | NO    |
| memory/performance_schema/events_statements_history                            | YES     | NO    |
| memory/performance_schema/events_statements_history.sqltext                    | YES     | NO    |
| memory/performance_schema/events_statements_history.tokens                     | YES     | NO    |
| memory/performance_schema/events_statements_history_long                       | YES     | NO    |
| memory/performance_schema/events_statements_history_long.sqltext               | YES     | NO    |
| memory/performance_schema/events_statements_history_long.tokens                | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_account_by_event_name   | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_digest                  | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_digest.tokens           | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_host_by_event_name      | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_program                 | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_thread_by_event_name    | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_user_by_event_name      | YES     | NO    |
| memory/performance_schema/events_statements_summary_global_by_event_name       | YES     | NO    |
| memory/performance_schema/events_transactions_history                          | YES     | NO    |
| memory/performance_schema/events_transactions_history_long                     | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_account_by_event_name | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_host_by_event_name    | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_thread_by_event_name  | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_user_by_event_name    | YES     | NO    |
| memory/performance_schema/events_waits_history                                 | YES     | NO    |
| memory/performance_schema/events_waits_history_long                            | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_account_by_event_name        | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_host_by_event_name           | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_thread_by_event_name         | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_user_by_event_name           | YES     | NO    |
| memory/performance_schema/file_class                                           | YES     | NO    |
| memory/performance_schema/file_handle                                          | YES     | NO    |
| memory/performance_schema/file_instances                                       | YES     | NO    |
| memory/performance_schema/hosts                                                | YES     | NO    |
| memory/performance_schema/memory_class                                         | YES     | NO    |
| memory/performance_schema/memory_summary_by_account_by_event_name              | YES     | NO    |
| memory/performance_schema/memory_summary_by_host_by_event_name                 | YES     | NO    |
| memory/performance_schema/memory_summary_by_thread_by_event_name               | YES     | NO    |
| memory/performance_schema/memory_summary_by_user_by_event_name                 | YES     | NO    |
| memory/performance_schema/memory_summary_global_by_event_name                  | YES     | NO    |
| memory/performance_schema/metadata_locks                                       | YES     | NO    |
| memory/performance_schema/mutex_class                                          | YES     | NO    |
| memory/performance_schema/mutex_instances                                      | YES     | NO    |
| memory/performance_schema/prepared_statements_instances                        | YES     | NO    |
| memory/performance_schema/rwlock_class                                         | YES     | NO    |
| memory/performance_schema/rwlock_instances                                     | YES     | NO    |
| memory/performance_schema/scalable_buffer                                      | YES     | NO    |
| memory/performance_schema/session_connect_attrs                                | YES     | NO    |
| memory/performance_schema/setup_actors                                         | YES     | NO    |
| memory/performance_schema/setup_objects                                        | YES     | NO    |
| memory/performance_schema/socket_class                                         | YES     | NO    |
| memory/performance_schema/socket_instances                                     | YES     | NO    |
| memory/performance_schema/stage_class                                          | YES     | NO    |
| memory/performance_schema/statement_class                                      | YES     | NO    |
| memory/performance_schema/table_handles                                        | YES     | NO    |
| memory/performance_schema/table_io_waits_summary_by_index_usage                | YES     | NO    |
| memory/performance_schema/table_lock_waits_summary_by_table                    | YES     | NO    |
| memory/performance_schema/table_shares                                         | YES     | NO    |
| memory/performance_schema/threads                                              | YES     | NO    |
| memory/performance_schema/thread_class                                         | YES     | NO    |
| memory/performance_schema/users                                                | YES     | NO    |
| memory/sql/acl_cache                                                           | NO      | NO    |
| memory/sql/binlog_cache_mngr                                                   | NO      | NO    |
| memory/sql/binlog_pos                                                          | NO      | NO    |
| memory/sql/binlog_statement_buffer                                             | NO      | NO    |
| memory/sql/binlog_ver_1_event                                                  | NO      | NO    |
| memory/sql/bison_stack                                                         | NO      | NO    |
| memory/sql/Blob_mem_storage::storage                                           | NO      | NO    |
| memory/sql/DATE_TIME_FORMAT                                                    | NO      | NO    |
| memory/sql/dboptions_hash                                                      | NO      | NO    |
| memory/sql/DDL_LOG_MEMORY_ENTRY                                                | NO      | NO    |
| memory/sql/display_table_locks                                                 | NO      | NO    |
| memory/sql/errmsgs                                                             | NO      | NO    |
| memory/sql/Event_basic::mem_root                                               | NO      | NO    |
| memory/sql/Event_queue_element_for_exec::names                                 | NO      | NO    |
| memory/sql/Event_scheduler::scheduler_param                                    | NO      | NO    |
| memory/sql/Filesort_info::merge                                                | NO      | NO    |
| memory/sql/Filesort_info::record_pointers                                      | NO      | NO    |
| memory/sql/frm::string                                                         | NO      | NO    |
| memory/sql/gdl                                                                 | NO      | NO    |
| memory/sql/Gis_read_stream::err_msg                                            | NO      | NO    |
| memory/sql/global_system_variables                                             | NO      | NO    |
| memory/sql/handler::errmsgs                                                    | NO      | NO    |
| memory/sql/handlerton                                                          | NO      | NO    |
| memory/sql/hash_index_key_buffer                                               | NO      | NO    |
| memory/sql/host_cache::hostname                                                | NO      | NO    |
| memory/sql/ignored_db                                                          | NO      | NO    |
| memory/sql/JOIN_CACHE                                                          | NO      | NO    |
| memory/sql/load_env_plugins                                                    | NO      | NO    |
| memory/sql/Locked_tables_list::m_locked_tables_root                            | NO      | NO    |
| memory/sql/MDL_context::acquire_locks                                          | NO      | NO    |
| memory/sql/MPVIO_EXT::auth_info                                                | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::basename                                             | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::index                                                | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::recover                                              | NO      | NO    |
| memory/sql/MYSQL_LOCK                                                          | NO      | NO    |
| memory/sql/MYSQL_LOG::name                                                     | NO      | NO    |
| memory/sql/mysql_plugin                                                        | NO      | NO    |
| memory/sql/mysql_plugin_dl                                                     | NO      | NO    |
| memory/sql/MYSQL_RELAY_LOG::basename                                           | NO      | NO    |
| memory/sql/MYSQL_RELAY_LOG::index                                              | NO      | NO    |
| memory/sql/my_str_malloc                                                       | NO      | NO    |
| memory/sql/NAMED_ILINK::name                                                   | NO      | NO    |
| memory/sql/native_functions                                                    | NO      | NO    |
| memory/sql/plugin_bookmark                                                     | NO      | NO    |
| memory/sql/plugin_int_mem_root                                                 | NO      | NO    |
| memory/sql/plugin_mem_root                                                     | NO      | NO    |
| memory/sql/Prepared_statement::main_mem_root                                   | NO      | NO    |
| memory/sql/Prepared_statement_map                                              | NO      | NO    |
| memory/sql/PROFILE                                                             | NO      | NO    |
| memory/sql/Query_cache                                                         | NO      | NO    |
| memory/sql/Queue::queue_item                                                   | NO      | NO    |
| memory/sql/QUICK_RANGE_SELECT::alloc                                           | NO      | NO    |
| memory/sql/QUICK_RANGE_SELECT::mrr_buf_desc                                    | NO      | NO    |
| memory/sql/Relay_log_info::group_relay_log_name                                | NO      | NO    |
| memory/sql/root                                                                | NO      | NO    |
| memory/sql/Row_data_memory::memory                                             | NO      | NO    |
| memory/sql/rpl_filter memory                                                   | NO      | NO    |
| memory/sql/Rpl_info_file::buffer                                               | NO      | NO    |
| memory/sql/servers_cache                                                       | NO      | NO    |
| memory/sql/SLAVE_INFO                                                          | NO      | NO    |
| memory/sql/Sort_param::tmp_buffer                                              | NO      | NO    |
| memory/sql/sp_head::call_mem_root                                              | NO      | NO    |
| memory/sql/sp_head::execute_mem_root                                           | NO      | NO    |
| memory/sql/sp_head::main_mem_root                                              | NO      | NO    |
| memory/sql/sql_acl_mem                                                         | NO      | NO    |
| memory/sql/sql_acl_memex                                                       | NO      | NO    |
| memory/sql/String::value                                                       | NO      | NO    |
| memory/sql/ST_SCHEMA_TABLE                                                     | NO      | NO    |
| memory/sql/Sys_var_charptr::value                                              | NO      | NO    |
| memory/sql/TABLE                                                               | NO      | NO    |
| memory/sql/table_mapping::m_mem_root                                           | NO      | NO    |
| memory/sql/TABLE_RULE_ENT                                                      | NO      | NO    |
| memory/sql/TABLE_SHARE::mem_root                                               | NO      | NO    |
| memory/sql/Table_triggers_list                                                 | NO      | NO    |
| memory/sql/Table_trigger_dispatcher::m_mem_root                                | NO      | NO    |
| memory/sql/TC_LOG_MMAP::pages                                                  | NO      | NO    |
| memory/sql/THD::db                                                             | NO      | NO    |
| memory/sql/THD::handler_tables_hash                                            | NO      | NO    |
| memory/sql/thd::main_mem_root                                                  | NO      | NO    |
| memory/sql/THD::sp_cache                                                       | NO      | NO    |
| memory/sql/THD::transactions::mem_root                                         | NO      | NO    |
| memory/sql/THD::variables                                                      | NO      | NO    |
| memory/sql/tz_storage                                                          | NO      | NO    |
| memory/sql/udf_mem                                                             | NO      | NO    |
| memory/sql/Unique::merge_buffer                                                | NO      | NO    |
| memory/sql/Unique::sort_buffer                                                 | NO      | NO    |
| memory/sql/user_conn                                                           | NO      | NO    |
| memory/sql/User_level_lock                                                     | NO      | NO    |
| memory/sql/user_var_entry                                                      | NO      | NO    |
| memory/sql/user_var_entry::value                                               | NO      | NO    |
| memory/sql/XID                                                                 | NO      | NO    |
| stage/aria/Waiting for a resource                                              | NO      | NO    |
| stage/innodb/alter table (end)                                                 | YES     | YES   |
| stage/innodb/alter table (insert)                                              | YES     | YES   |
| stage/innodb/alter table (log apply index)                                     | YES     | YES   |
| stage/innodb/alter table (log apply table)                                     | YES     | YES   |
| stage/innodb/alter table (merge sort)                                          | YES     | YES   |
| stage/innodb/alter table (read PK and internal sort)                           | YES     | YES   |
| stage/innodb/buffer pool load                                                  | YES     | YES   |
| stage/mysys/Waiting for table level lock                                       | NO      | NO    |
| stage/sql/After apply log event                                                | NO      | NO    |
| stage/sql/After create                                                         | NO      | NO    |
| stage/sql/After opening tables                                                 | NO      | NO    |
| stage/sql/After table lock                                                     | NO      | NO    |
| stage/sql/Allocating local table                                               | NO      | NO    |
| stage/sql/altering table                                                       | NO      | NO    |
| stage/sql/Apply log event                                                      | NO      | NO    |
| stage/sql/Changing master                                                      | NO      | NO    |
| stage/sql/Checking master version                                              | NO      | NO    |
| stage/sql/checking permissions                                                 | NO      | NO    |
| stage/sql/checking privileges on cached query                                  | NO      | NO    |
| stage/sql/Checking query cache for query                                       | NO      | NO    |
| stage/sql/closing tables                                                       | NO      | NO    |
| stage/sql/Commit                                                               | NO      | NO    |
| stage/sql/Commit implicit                                                      | NO      | NO    |
| stage/sql/Committing alter table to storage engine                             | NO      | NO    |
| stage/sql/Connecting to master                                                 | NO      | NO    |
| stage/sql/Converting HEAP to Aria                                              | NO      | NO    |
| stage/sql/copy to tmp table                                                    | YES     | YES   |
| stage/sql/Copying to group table                                               | NO      | NO    |
| stage/sql/Copying to tmp table                                                 | NO      | NO    |
| stage/sql/Creating delayed handler                                             | NO      | NO    |
| stage/sql/Creating sort index                                                  | NO      | NO    |
| stage/sql/creating table                                                       | NO      | NO    |
| stage/sql/Creating tmp table                                                   | NO      | NO    |
| stage/sql/Deleting from main table                                             | NO      | NO    |
| stage/sql/Deleting from reference tables                                       | NO      | NO    |
| stage/sql/Discard_or_import_tablespace                                         | NO      | NO    |
| stage/sql/Enabling keys                                                        | NO      | NO    |
| stage/sql/End of update loop                                                   | NO      | NO    |
| stage/sql/Executing                                                            | NO      | NO    |
| stage/sql/Execution of init_command                                            | NO      | NO    |
| stage/sql/Explaining                                                           | NO      | NO    |
| stage/sql/Filling schema table                                                 | NO      | NO    |
| stage/sql/Finding key cache                                                    | NO      | NO    |
| stage/sql/Finished reading one binlog; switching to next binlog                | NO      | NO    |
| stage/sql/Flushing relay log and master info repository.                       | NO      | NO    |
| stage/sql/Flushing relay-log info file.                                        | NO      | NO    |
| stage/sql/Freeing items                                                        | NO      | NO    |
| stage/sql/Fulltext initialization                                              | NO      | NO    |
| stage/sql/Got handler lock                                                     | NO      | NO    |
| stage/sql/Got old table                                                        | NO      | NO    |
| stage/sql/init                                                                 | NO      | NO    |
| stage/sql/init for update                                                      | NO      | NO    |
| stage/sql/Insert                                                               | NO      | NO    |
| stage/sql/Invalidating query cache entries (table list)                        | NO      | NO    |
| stage/sql/Invalidating query cache entries (table)                             | NO      | NO    |
| stage/sql/Killing slave                                                        | NO      | NO    |
| stage/sql/Logging slow query                                                   | NO      | NO    |
| stage/sql/Making temporary file (append) before replaying LOAD DATA INFILE     | NO      | NO    |
| stage/sql/Making temporary file (create) before replaying LOAD DATA INFILE     | NO      | NO    |
| stage/sql/Manage keys                                                          | NO      | NO    |
| stage/sql/Master has sent all binlog to slave; waiting for more updates        | NO      | NO    |
| stage/sql/Opening tables                                                       | NO      | NO    |
| stage/sql/Optimizing                                                           | NO      | NO    |
| stage/sql/Preparing                                                            | NO      | NO    |
| stage/sql/preparing for alter table                                            | NO      | NO    |
| stage/sql/Processing binlog checkpoint notification                            | NO      | NO    |
| stage/sql/Processing requests                                                  | NO      | NO    |
| stage/sql/Purging old relay logs                                               | NO      | NO    |
| stage/sql/Query end                                                            | NO      | NO    |
| stage/sql/Queueing master event to the relay log                               | NO      | NO    |
| stage/sql/Reading event from the relay log                                     | NO      | NO    |
| stage/sql/Reading semi-sync ACK from slave                                     | NO      | NO    |
| stage/sql/Recreating table                                                     | NO      | NO    |
| stage/sql/Registering slave on master                                          | NO      | NO    |
| stage/sql/Removing duplicates                                                  | NO      | NO    |
| stage/sql/Removing tmp table                                                   | NO      | NO    |
| stage/sql/Rename                                                               | NO      | NO    |
| stage/sql/Rename result table                                                  | NO      | NO    |
| stage/sql/Requesting binlog dump                                               | NO      | NO    |
| stage/sql/Reschedule                                                           | NO      | NO    |
| stage/sql/Reset for next command                                               | NO      | NO    |
| stage/sql/Rollback                                                             | NO      | NO    |
| stage/sql/Rollback_implicit                                                    | NO      | NO    |
| stage/sql/Searching rows for update                                            | NO      | NO    |
| stage/sql/Sending binlog event to slave                                        | NO      | NO    |
| stage/sql/Sending cached result to client                                      | NO      | NO    |
| stage/sql/Sending data                                                         | NO      | NO    |
| stage/sql/setup                                                                | NO      | NO    |
| stage/sql/Show explain                                                         | NO      | NO    |
| stage/sql/Slave has read all relay log; waiting for more updates               | NO      | NO    |
| stage/sql/Sorting                                                              | NO      | NO    |
| stage/sql/Sorting for group                                                    | NO      | NO    |
| stage/sql/Sorting for order                                                    | NO      | NO    |
| stage/sql/Sorting result                                                       | NO      | NO    |
| stage/sql/starting                                                             | NO      | NO    |
| stage/sql/Starting cleanup                                                     | NO      | NO    |
| stage/sql/Statistics                                                           | NO      | NO    |
| stage/sql/Stopping binlog background thread                                    | NO      | NO    |
| stage/sql/Storing result in query cache                                        | NO      | NO    |
| stage/sql/Storing row into queue                                               | NO      | NO    |
| stage/sql/System lock                                                          | NO      | NO    |
| stage/sql/table lock                                                           | NO      | NO    |
| stage/sql/Unlocking tables                                                     | NO      | NO    |
| stage/sql/Update                                                               | NO      | NO    |
| stage/sql/Updating                                                             | NO      | NO    |
| stage/sql/Updating main table                                                  | NO      | NO    |
| stage/sql/Updating reference tables                                            | NO      | NO    |
| stage/sql/Upgrading lock                                                       | NO      | NO    |
| stage/sql/User lock                                                            | NO      | NO    |
| stage/sql/User sleep                                                           | NO      | NO    |
| stage/sql/Verifying table                                                      | NO      | NO    |
| stage/sql/Waiting for background binlog tasks                                  | NO      | NO    |
| stage/sql/Waiting for backup lock                                              | NO      | NO    |
| stage/sql/Waiting for delay_list                                               | NO      | NO    |
| stage/sql/Waiting for event metadata lock                                      | NO      | NO    |
| stage/sql/Waiting for GTID to be written to binary log                         | NO      | NO    |
| stage/sql/Waiting for handler insert                                           | NO      | NO    |
| stage/sql/Waiting for handler lock                                             | NO      | NO    |
| stage/sql/Waiting for handler open                                             | NO      | NO    |
| stage/sql/Waiting for INSERT                                                   | NO      | NO    |
| stage/sql/Waiting for master to send event                                     | NO      | NO    |
| stage/sql/Waiting for master update                                            | NO      | NO    |
| stage/sql/Waiting for next activation                                          | NO      | NO    |
| stage/sql/Waiting for other master connection to process the same GTID         | NO      | NO    |
| stage/sql/Waiting for parallel replication deadlock handling to complete       | NO      | NO    |
| stage/sql/Waiting for prior transaction to commit                              | NO      | NO    |
| stage/sql/Waiting for prior transaction to start commit                        | NO      | NO    |
| stage/sql/Waiting for query cache lock                                         | NO      | NO    |
| stage/sql/Waiting for requests                                                 | NO      | NO    |
| stage/sql/Waiting for room in worker thread event queue                        | NO      | NO    |
| stage/sql/Waiting for schema metadata lock                                     | NO      | NO    |
| stage/sql/Waiting for semi-sync ACK from slave                                 | NO      | NO    |
| stage/sql/Waiting for semi-sync slave connection                               | NO      | NO    |
| stage/sql/Waiting for slave mutex on exit                                      | NO      | NO    |
| stage/sql/Waiting for slave thread to start                                    | NO      | NO    |
| stage/sql/Waiting for stored function metadata lock                            | NO      | NO    |
| stage/sql/Waiting for stored package body metadata lock                        | NO      | NO    |
| stage/sql/Waiting for stored procedure metadata lock                           | NO      | NO    |
| stage/sql/Waiting for table flush                                              | NO      | NO    |
| stage/sql/Waiting for table metadata lock                                      | NO      | NO    |
| stage/sql/Waiting for the next event in relay log                              | NO      | NO    |
| stage/sql/Waiting for the scheduler to stop                                    | NO      | NO    |
| stage/sql/Waiting for the slave SQL thread to advance position                 | NO      | NO    |
| stage/sql/Waiting for the slave SQL thread to free enough relay log space      | NO      | NO    |
| stage/sql/Waiting for trigger metadata lock                                    | NO      | NO    |
| stage/sql/Waiting for work from SQL thread                                     | NO      | NO    |
| stage/sql/Waiting in MASTER_GTID_WAIT()                                        | NO      | NO    |
| stage/sql/Waiting in MASTER_GTID_WAIT() (primary waiter)                       | NO      | NO    |
| stage/sql/Waiting on empty queue                                               | NO      | NO    |
| stage/sql/Waiting to finalize termination                                      | NO      | NO    |
| stage/sql/Waiting until MASTER_DELAY seconds after master executed event       | NO      | NO    |
| stage/sql/Writing to binlog                                                    | NO      | NO    |
| statement/abstract/new_packet                                                  | YES     | YES   |
| statement/abstract/Query                                                       | YES     | YES   |
| statement/abstract/relay_log                                                   | YES     | YES   |
| statement/com/Binlog Dump                                                      | YES     | YES   |
| statement/com/Bulk_execute                                                     | YES     | YES   |
| statement/com/Change user                                                      | YES     | YES   |
| statement/com/Close stmt                                                       | YES     | YES   |
| statement/com/Com_multi                                                        | YES     | YES   |
| statement/com/Connect                                                          | YES     | YES   |
| statement/com/Connect Out                                                      | YES     | YES   |
| statement/com/Create DB                                                        | YES     | YES   |
| statement/com/Daemon                                                           | YES     | YES   |
| statement/com/Debug                                                            | YES     | YES   |
| statement/com/Delayed insert                                                   | YES     | YES   |
| statement/com/Drop DB                                                          | YES     | YES   |
| statement/com/Error                                                            | YES     | YES   |
| statement/com/Execute                                                          | YES     | YES   |
| statement/com/Fetch                                                            | YES     | YES   |
| statement/com/Field List                                                       | YES     | YES   |
| statement/com/Init DB                                                          | YES     | YES   |
| statement/com/Kill                                                             | YES     | YES   |
| statement/com/Long Data                                                        | YES     | YES   |
| statement/com/Ping                                                             | YES     | YES   |
| statement/com/Prepare                                                          | YES     | YES   |
| statement/com/Processlist                                                      | YES     | YES   |
| statement/com/Quit                                                             | YES     | YES   |
| statement/com/Refresh                                                          | YES     | YES   |
| statement/com/Register Slave                                                   | YES     | YES   |
| statement/com/Reset connection                                                 | YES     | YES   |
| statement/com/Reset stmt                                                       | YES     | YES   |
| statement/com/Set option                                                       | YES     | YES   |
| statement/com/Shutdown                                                         | YES     | YES   |
| statement/com/Slave_IO                                                         | YES     | YES   |
| statement/com/Slave_SQL                                                        | YES     | YES   |
| statement/com/Slave_worker                                                     | YES     | YES   |
| statement/com/Sleep                                                            | YES     | YES   |
| statement/com/Statistics                                                       | YES     | YES   |
| statement/com/Table Dump                                                       | YES     | YES   |
| statement/com/Time                                                             | YES     | YES   |
| statement/com/Unimpl get tid                                                   | YES     | YES   |
| statement/scheduler/event                                                      | YES     | YES   |
| statement/sp/agg_cfetch                                                        | YES     | YES   |
| statement/sp/cclose                                                            | YES     | YES   |
| statement/sp/cfetch                                                            | YES     | YES   |
| statement/sp/copen                                                             | YES     | YES   |
| statement/sp/cpop                                                              | YES     | YES   |
| statement/sp/cpush                                                             | YES     | YES   |
| statement/sp/cursor_copy_struct                                                | YES     | YES   |
| statement/sp/error                                                             | YES     | YES   |
| statement/sp/freturn                                                           | YES     | YES   |
| statement/sp/hpop                                                              | YES     | YES   |
| statement/sp/hpush_jump                                                        | YES     | YES   |
| statement/sp/hreturn                                                           | YES     | YES   |
| statement/sp/jump                                                              | YES     | YES   |
| statement/sp/jump_if_not                                                       | YES     | YES   |
| statement/sp/preturn                                                           | YES     | YES   |
| statement/sp/set                                                               | YES     | YES   |
| statement/sp/set_case_expr                                                     | YES     | YES   |
| statement/sp/set_trigger_field                                                 | YES     | YES   |
| statement/sp/stmt                                                              | YES     | YES   |
| statement/sql/                                                                 | YES     | YES   |
| statement/sql/alter_db                                                         | YES     | YES   |
| statement/sql/alter_db_upgrade                                                 | YES     | YES   |
| statement/sql/alter_event                                                      | YES     | YES   |
| statement/sql/alter_function                                                   | YES     | YES   |
| statement/sql/alter_procedure                                                  | YES     | YES   |
| statement/sql/alter_sequence                                                   | YES     | YES   |
| statement/sql/alter_server                                                     | YES     | YES   |
| statement/sql/alter_table                                                      | YES     | YES   |
| statement/sql/alter_tablespace                                                 | YES     | YES   |
| statement/sql/alter_user                                                       | YES     | YES   |
| statement/sql/analyze                                                          | YES     | YES   |
| statement/sql/assign_to_keycache                                               | YES     | YES   |
| statement/sql/backup                                                           | YES     | YES   |
| statement/sql/backup_lock                                                      | YES     | YES   |
| statement/sql/begin                                                            | YES     | YES   |
| statement/sql/binlog                                                           | YES     | YES   |
| statement/sql/call_procedure                                                   | YES     | YES   |
| statement/sql/change_db                                                        | YES     | YES   |
| statement/sql/change_master                                                    | YES     | YES   |
| statement/sql/check                                                            | YES     | YES   |
| statement/sql/checksum                                                         | YES     | YES   |
| statement/sql/commit                                                           | YES     | YES   |
| statement/sql/compound_sql                                                     | YES     | YES   |
| statement/sql/create_db                                                        | YES     | YES   |
| statement/sql/create_event                                                     | YES     | YES   |
| statement/sql/create_function                                                  | YES     | YES   |
| statement/sql/create_index                                                     | YES     | YES   |
| statement/sql/create_package                                                   | YES     | YES   |
| statement/sql/create_package_body                                              | YES     | YES   |
| statement/sql/create_procedure                                                 | YES     | YES   |
| statement/sql/create_role                                                      | YES     | YES   |
| statement/sql/create_sequence                                                  | YES     | YES   |
| statement/sql/create_server                                                    | YES     | YES   |
| statement/sql/create_table                                                     | YES     | YES   |
| statement/sql/create_trigger                                                   | YES     | YES   |
| statement/sql/create_udf                                                       | YES     | YES   |
| statement/sql/create_user                                                      | YES     | YES   |
| statement/sql/create_view                                                      | YES     | YES   |
| statement/sql/dealloc_sql                                                      | YES     | YES   |
| statement/sql/delete                                                           | YES     | YES   |
| statement/sql/delete_multi                                                     | YES     | YES   |
| statement/sql/do                                                               | YES     | YES   |
| statement/sql/drop_db                                                          | YES     | YES   |
| statement/sql/drop_event                                                       | YES     | YES   |
| statement/sql/drop_function                                                    | YES     | YES   |
| statement/sql/drop_index                                                       | YES     | YES   |
| statement/sql/drop_package                                                     | YES     | YES   |
| statement/sql/drop_package_body                                                | YES     | YES   |
| statement/sql/drop_procedure                                                   | YES     | YES   |
| statement/sql/drop_role                                                        | YES     | YES   |
| statement/sql/drop_sequence                                                    | YES     | YES   |
| statement/sql/drop_server                                                      | YES     | YES   |
| statement/sql/drop_table                                                       | YES     | YES   |
| statement/sql/drop_trigger                                                     | YES     | YES   |
| statement/sql/drop_user                                                        | YES     | YES   |
| statement/sql/drop_view                                                        | YES     | YES   |
| statement/sql/empty_query                                                      | YES     | YES   |
| statement/sql/error                                                            | YES     | YES   |
| statement/sql/execute_immediate                                                | YES     | YES   |
| statement/sql/execute_sql                                                      | YES     | YES   |
| statement/sql/flush                                                            | YES     | YES   |
| statement/sql/get_diagnostics                                                  | YES     | YES   |
| statement/sql/grant                                                            | YES     | YES   |
| statement/sql/grant_role                                                       | YES     | YES   |
| statement/sql/ha_close                                                         | YES     | YES   |
| statement/sql/ha_open                                                          | YES     | YES   |
| statement/sql/ha_read                                                          | YES     | YES   |
| statement/sql/help                                                             | YES     | YES   |
| statement/sql/insert                                                           | YES     | YES   |
| statement/sql/insert_select                                                    | YES     | YES   |
| statement/sql/install_plugin                                                   | YES     | YES   |
| statement/sql/kill                                                             | YES     | YES   |
| statement/sql/load                                                             | YES     | YES   |
| statement/sql/lock_tables                                                      | YES     | YES   |
| statement/sql/optimize                                                         | YES     | YES   |
| statement/sql/preload_keys                                                     | YES     | YES   |
| statement/sql/prepare_sql                                                      | YES     | YES   |
| statement/sql/purge                                                            | YES     | YES   |
| statement/sql/purge_before_date                                                | YES     | YES   |
| statement/sql/release_savepoint                                                | YES     | YES   |
| statement/sql/rename_table                                                     | YES     | YES   |
| statement/sql/rename_user                                                      | YES     | YES   |
| statement/sql/repair                                                           | YES     | YES   |
| statement/sql/replace                                                          | YES     | YES   |
| statement/sql/replace_select                                                   | YES     | YES   |
| statement/sql/reset                                                            | YES     | YES   |
| statement/sql/resignal                                                         | YES     | YES   |
| statement/sql/revoke                                                           | YES     | YES   |
| statement/sql/revoke_all                                                       | YES     | YES   |
| statement/sql/revoke_role                                                      | YES     | YES   |
| statement/sql/rollback                                                         | YES     | YES   |
| statement/sql/rollback_to_savepoint                                            | YES     | YES   |
| statement/sql/savepoint                                                        | YES     | YES   |
| statement/sql/select                                                           | YES     | YES   |
| statement/sql/set_option                                                       | YES     | YES   |
| statement/sql/show_authors                                                     | YES     | YES   |
| statement/sql/show_binlogs                                                     | YES     | YES   |
| statement/sql/show_binlog_events                                               | YES     | YES   |
| statement/sql/show_binlog_status                                               | YES     | YES   |
| statement/sql/show_charsets                                                    | YES     | YES   |
| statement/sql/show_collations                                                  | YES     | YES   |
| statement/sql/show_contributors                                                | YES     | YES   |
| statement/sql/show_create_db                                                   | YES     | YES   |
| statement/sql/show_create_event                                                | YES     | YES   |
| statement/sql/show_create_func                                                 | YES     | YES   |
| statement/sql/show_create_package                                              | YES     | YES   |
| statement/sql/show_create_package_body                                         | YES     | YES   |
| statement/sql/show_create_proc                                                 | YES     | YES   |
| statement/sql/show_create_table                                                | YES     | YES   |
| statement/sql/show_create_trigger                                              | YES     | YES   |
| statement/sql/show_create_user                                                 | YES     | YES   |
| statement/sql/show_databases                                                   | YES     | YES   |
| statement/sql/show_engine_logs                                                 | YES     | YES   |
| statement/sql/show_engine_mutex                                                | YES     | YES   |
| statement/sql/show_engine_status                                               | YES     | YES   |
| statement/sql/show_errors                                                      | YES     | YES   |
| statement/sql/show_events                                                      | YES     | YES   |
| statement/sql/show_explain                                                     | YES     | YES   |
| statement/sql/show_fields                                                      | YES     | YES   |
| statement/sql/show_function_status                                             | YES     | YES   |
| statement/sql/show_generic                                                     | YES     | YES   |
| statement/sql/show_grants                                                      | YES     | YES   |
| statement/sql/show_keys                                                        | YES     | YES   |
| statement/sql/show_open_tables                                                 | YES     | YES   |
| statement/sql/show_package_body_status                                         | YES     | YES   |
| statement/sql/show_package_status                                              | YES     | YES   |
| statement/sql/show_plugins                                                     | YES     | YES   |
| statement/sql/show_privileges                                                  | YES     | YES   |
| statement/sql/show_procedure_status                                            | YES     | YES   |
| statement/sql/show_processlist                                                 | YES     | YES   |
| statement/sql/show_profile                                                     | YES     | YES   |
| statement/sql/show_profiles                                                    | YES     | YES   |
| statement/sql/show_relaylog_events                                             | YES     | YES   |
| statement/sql/show_slave_hosts                                                 | YES     | YES   |
| statement/sql/show_slave_status                                                | YES     | YES   |
| statement/sql/show_status                                                      | YES     | YES   |
| statement/sql/show_storage_engines                                             | YES     | YES   |
| statement/sql/show_tables                                                      | YES     | YES   |
| statement/sql/show_table_status                                                | YES     | YES   |
| statement/sql/show_triggers                                                    | YES     | YES   |
| statement/sql/show_variables                                                   | YES     | YES   |
| statement/sql/show_warnings                                                    | YES     | YES   |
| statement/sql/shutdown                                                         | YES     | YES   |
| statement/sql/signal                                                           | YES     | YES   |
| statement/sql/start_all_slaves                                                 | YES     | YES   |
| statement/sql/start_slave                                                      | YES     | YES   |
| statement/sql/stop_all_slaves                                                  | YES     | YES   |
| statement/sql/stop_slave                                                       | YES     | YES   |
| statement/sql/truncate                                                         | YES     | YES   |
| statement/sql/uninstall_plugin                                                 | YES     | YES   |
| statement/sql/unlock_tables                                                    | YES     | YES   |
| statement/sql/update                                                           | YES     | YES   |
| statement/sql/update_multi                                                     | YES     | YES   |
| statement/sql/xa_commit                                                        | YES     | YES   |
| statement/sql/xa_end                                                           | YES     | YES   |
| statement/sql/xa_prepare                                                       | YES     | YES   |
| statement/sql/xa_recover                                                       | YES     | YES   |
| statement/sql/xa_rollback                                                      | YES     | YES   |
| statement/sql/xa_start                                                         | YES     | YES   |
| transaction                                                                    | NO      | NO    |
| wait/io/file/aria/control                                                      | YES     | YES   |
| wait/io/file/aria/MAD                                                          | YES     | YES   |
| wait/io/file/aria/MAI                                                          | YES     | YES   |
| wait/io/file/aria/translog                                                     | YES     | YES   |
| wait/io/file/csv/data                                                          | YES     | YES   |
| wait/io/file/csv/metadata                                                      | YES     | YES   |
| wait/io/file/csv/update                                                        | YES     | YES   |
| wait/io/file/innodb/innodb_data_file                                           | YES     | YES   |
| wait/io/file/innodb/innodb_log_file                                            | YES     | YES   |
| wait/io/file/innodb/innodb_temp_file                                           | YES     | YES   |
| wait/io/file/myisam/data_tmp                                                   | YES     | YES   |
| wait/io/file/myisam/dfile                                                      | YES     | YES   |
| wait/io/file/myisam/kfile                                                      | YES     | YES   |
| wait/io/file/myisam/log                                                        | YES     | YES   |
| wait/io/file/myisammrg/MRG                                                     | YES     | YES   |
| wait/io/file/mysys/charset                                                     | YES     | YES   |
| wait/io/file/mysys/cnf                                                         | YES     | YES   |
| wait/io/file/partition/ha_partition::parfile                                   | YES     | YES   |
| wait/io/file/sql/binlog                                                        | YES     | YES   |
| wait/io/file/sql/binlog_cache                                                  | YES     | YES   |
| wait/io/file/sql/binlog_index                                                  | YES     | YES   |
| wait/io/file/sql/binlog_index_cache                                            | YES     | YES   |
| wait/io/file/sql/binlog_state                                                  | YES     | YES   |
| wait/io/file/sql/casetest                                                      | YES     | YES   |
| wait/io/file/sql/dbopt                                                         | YES     | YES   |
| wait/io/file/sql/des_key_file                                                  | YES     | YES   |
| wait/io/file/sql/ERRMSG                                                        | YES     | YES   |
| wait/io/file/sql/file_parser                                                   | YES     | YES   |
| wait/io/file/sql/FRM                                                           | YES     | YES   |
| wait/io/file/sql/global_ddl_log                                                | YES     | YES   |
| wait/io/file/sql/init                                                          | YES     | YES   |
| wait/io/file/sql/io_cache                                                      | YES     | YES   |
| wait/io/file/sql/load                                                          | YES     | YES   |
| wait/io/file/sql/LOAD_FILE                                                     | YES     | YES   |
| wait/io/file/sql/log_event_data                                                | YES     | YES   |
| wait/io/file/sql/log_event_info                                                | YES     | YES   |
| wait/io/file/sql/map                                                           | YES     | YES   |
| wait/io/file/sql/master_info                                                   | YES     | YES   |
| wait/io/file/sql/misc                                                          | YES     | YES   |
| wait/io/file/sql/partition_ddl_log                                             | YES     | YES   |
| wait/io/file/sql/pid                                                           | YES     | YES   |
| wait/io/file/sql/query_log                                                     | YES     | YES   |
| wait/io/file/sql/relaylog                                                      | YES     | YES   |
| wait/io/file/sql/relaylog_cache                                                | YES     | YES   |
| wait/io/file/sql/relaylog_index                                                | YES     | YES   |
| wait/io/file/sql/relaylog_index_cache                                          | YES     | YES   |
| wait/io/file/sql/relay_log_info                                                | YES     | YES   |
| wait/io/file/sql/select_to_file                                                | YES     | YES   |
| wait/io/file/sql/send_file                                                     | YES     | YES   |
| wait/io/file/sql/slow_log                                                      | YES     | YES   |
| wait/io/file/sql/tclog                                                         | YES     | YES   |
| wait/io/file/sql/trigger                                                       | YES     | YES   |
| wait/io/file/sql/trigger_name                                                  | YES     | YES   |
| wait/io/file/sql/wsrep_gra_log                                                 | YES     | YES   |
| wait/io/socket/sql/client_connection                                           | NO      | NO    |
| wait/io/socket/sql/server_tcpip_socket                                         | NO      | NO    |
| wait/io/socket/sql/server_unix_socket                                          | NO      | NO    |
| wait/io/table/sql/handler                                                      | YES     | YES   |
| wait/lock/metadata/sql/mdl                                                     | NO      | NO    |
| wait/lock/table/sql/handler                                                    | YES     | YES   |
| wait/synch/cond/aria/BITMAP::bitmap_cond                                       | NO      | NO    |
| wait/synch/cond/aria/COND_soft_sync                                            | NO      | NO    |
| wait/synch/cond/aria/SERVICE_THREAD_CONTROL::COND_control                      | NO      | NO    |
| wait/synch/cond/aria/SHARE::key_del_cond                                       | NO      | NO    |
| wait/synch/cond/aria/SORT_INFO::cond                                           | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_BUFFER::prev_sent_to_disk_cond                   | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_BUFFER::waiting_filling_buffer                   | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_DESCRIPTOR::log_flush_cond                       | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_DESCRIPTOR::new_goal_cond                        | NO      | NO    |
| wait/synch/cond/innodb/commit_cond                                             | NO      | NO    |
| wait/synch/cond/myisam/MI_SORT_INFO::cond                                      | NO      | NO    |
| wait/synch/cond/mysys/COND_alarm                                               | NO      | NO    |
| wait/synch/cond/mysys/COND_timer                                               | NO      | NO    |
| wait/synch/cond/mysys/IO_CACHE_SHARE::cond                                     | NO      | NO    |
| wait/synch/cond/mysys/IO_CACHE_SHARE::cond_writer                              | NO      | NO    |
| wait/synch/cond/mysys/my_thread_var::suspend                                   | NO      | NO    |
| wait/synch/cond/mysys/THR_COND_threads                                         | NO      | NO    |
| wait/synch/cond/mysys/WT_RESOURCE::cond                                        | NO      | NO    |
| wait/synch/cond/sql/Ack_receiver::cond                                         | NO      | NO    |
| wait/synch/cond/sql/COND_binlog_send                                           | NO      | NO    |
| wait/synch/cond/sql/COND_flush_thread_cache                                    | NO      | NO    |
| wait/synch/cond/sql/COND_group_commit_orderer                                  | NO      | NO    |
| wait/synch/cond/sql/COND_gtid_ignore_duplicates                                | NO      | NO    |
| wait/synch/cond/sql/COND_manager                                               | NO      | NO    |
| wait/synch/cond/sql/COND_parallel_entry                                        | NO      | NO    |
| wait/synch/cond/sql/COND_prepare_ordered                                       | NO      | NO    |
| wait/synch/cond/sql/COND_queue_state                                           | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread                                            | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_pool                                       | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_queue                                      | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_stop                                       | NO      | NO    |
| wait/synch/cond/sql/COND_server_started                                        | NO      | NO    |
| wait/synch/cond/sql/COND_slave_background                                      | NO      | NO    |
| wait/synch/cond/sql/COND_start_thread                                          | NO      | NO    |
| wait/synch/cond/sql/COND_thread_cache                                          | NO      | NO    |
| wait/synch/cond/sql/COND_wait_gtid                                             | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_donor_monitor                                   | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_gtid_wait_upto                                  | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_joiner_monitor                                  | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_ready                                           | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_replaying                                       | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_sst                                             | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_sst_init                                        | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_wsrep_slave_threads                             | NO      | NO    |
| wait/synch/cond/sql/Delayed_insert::cond                                       | NO      | NO    |
| wait/synch/cond/sql/Delayed_insert::cond_client                                | NO      | NO    |
| wait/synch/cond/sql/Event_scheduler::COND_state                                | NO      | NO    |
| wait/synch/cond/sql/Item_func_sleep::cond                                      | NO      | NO    |
| wait/synch/cond/sql/Master_info::data_cond                                     | NO      | NO    |
| wait/synch/cond/sql/Master_info::sleep_cond                                    | NO      | NO    |
| wait/synch/cond/sql/Master_info::start_cond                                    | NO      | NO    |
| wait/synch/cond/sql/Master_info::stop_cond                                     | NO      | NO    |
| wait/synch/cond/sql/MDL_context::COND_wait_status                              | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_binlog_background_thread               | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_binlog_background_thread_end           | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_bin_log_updated                        | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_queue_busy                             | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_relay_log_updated                      | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_xid_list                               | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_bin_log_updated                      | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_queue_busy                           | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_relay_log_updated                    | NO      | NO    |
| wait/synch/cond/sql/PAGE::cond                                                 | NO      | NO    |
| wait/synch/cond/sql/Query_cache::COND_cache_status_changed                     | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::data_cond                                  | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::log_space_cond                             | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::start_cond                                 | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::stop_cond                                  | NO      | NO    |
| wait/synch/cond/sql/Rpl_group_info::sleep_cond                                 | NO      | NO    |
| wait/synch/cond/sql/show_explain                                               | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::cond                                          | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::COND_rotation                                 | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::tdc.COND_release                              | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_active                                   | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_pool                                     | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_queue_busy                               | NO      | NO    |
| wait/synch/cond/sql/THD::COND_wakeup_ready                                     | NO      | NO    |
| wait/synch/cond/sql/THD::COND_wsrep_thd                                        | NO      | NO    |
| wait/synch/cond/sql/User_level_lock::cond                                      | NO      | NO    |
| wait/synch/cond/sql/wait_for_commit::COND_wait_commit                          | NO      | NO    |
| wait/synch/cond/sql/wsrep_sst_thread                                           | NO      | NO    |
| wait/synch/mutex/aria/LOCK_soft_sync                                           | NO      | NO    |
| wait/synch/mutex/aria/LOCK_trn_list                                            | NO      | NO    |
| wait/synch/mutex/aria/PAGECACHE::cache_lock                                    | NO      | NO    |
| wait/synch/mutex/aria/SERVICE_THREAD_CONTROL::LOCK_control                     | NO      | NO    |
| wait/synch/mutex/aria/SHARE::bitmap::bitmap_lock                               | NO      | NO    |
| wait/synch/mutex/aria/SHARE::close_lock                                        | NO      | NO    |
| wait/synch/mutex/aria/SHARE::intern_lock                                       | NO      | NO    |
| wait/synch/mutex/aria/SHARE::key_del_lock                                      | NO      | NO    |
| wait/synch/mutex/aria/SORT_INFO::mutex                                         | NO      | NO    |
| wait/synch/mutex/aria/THR_LOCK_maria                                           | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_BUFFER::mutex                                   | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::dirty_buffer_mask_lock              | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::file_header_lock                    | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::log_flush_lock                      | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::purger_lock                         | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::sent_to_disk_lock                   | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::unfinished_files_lock               | NO      | NO    |
| wait/synch/mutex/aria/TRN::state_lock                                          | NO      | NO    |
| wait/synch/mutex/csv/tina                                                      | NO      | NO    |
| wait/synch/mutex/csv/TINA_SHARE::mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/buf_dblwr_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/buf_pool_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/commit_cond_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/dict_foreign_err_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/dict_sys_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/fil_system_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/flush_list_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/fts_delete_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/fts_doc_id_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_bitmap_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_mutex                                             | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_pessimistic_insert_mutex                          | NO      | NO    |
| wait/synch/mutex/innodb/lock_mutex                                             | NO      | NO    |
| wait/synch/mutex/innodb/lock_wait_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/log_flush_order_mutex                                  | NO      | NO    |
| wait/synch/mutex/innodb/log_sys_mutex                                          | NO      | NO    |
| wait/synch/mutex/innodb/noredo_rseg_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/page_zip_stat_per_index_mutex                          | NO      | NO    |
| wait/synch/mutex/innodb/pending_checkpoint_mutex                               | NO      | NO    |
| wait/synch/mutex/innodb/purge_sys_pq_mutex                                     | NO      | NO    |
| wait/synch/mutex/innodb/recalc_pool_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/recv_sys_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/redo_rseg_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/rtr_active_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/rtr_match_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/rtr_path_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/rw_lock_list_mutex                                     | NO      | NO    |
| wait/synch/mutex/innodb/srv_innodb_monitor_mutex                               | NO      | NO    |
| wait/synch/mutex/innodb/srv_misc_tmpfile_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/srv_monitor_file_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/srv_threads_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/trx_mutex                                              | NO      | NO    |
| wait/synch/mutex/innodb/trx_pool_manager_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/trx_pool_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/trx_sys_mutex                                          | NO      | NO    |
| wait/synch/mutex/myisam/MI_CHECK::print_msg                                    | NO      | NO    |
| wait/synch/mutex/myisam/MI_SORT_INFO::mutex                                    | NO      | NO    |
| wait/synch/mutex/myisam/MYISAM_SHARE::intern_lock                              | NO      | NO    |
| wait/synch/mutex/myisammrg/MYRG_INFO::mutex                                    | NO      | NO    |
| wait/synch/mutex/mysys/BITMAP::mutex                                           | NO      | NO    |
| wait/synch/mutex/mysys/IO_CACHE::append_buffer_lock                            | NO      | NO    |
| wait/synch/mutex/mysys/IO_CACHE::SHARE_mutex                                   | NO      | NO    |
| wait/synch/mutex/mysys/KEY_CACHE::cache_lock                                   | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_alarm                                              | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_timer                                              | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_uuid_generator                                     | NO      | NO    |
| wait/synch/mutex/mysys/my_thread_var::mutex                                    | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK::mutex                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_charset                                        | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_heap                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_lock                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_malloc                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_myisam                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_myisam_mmap                                    | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_net                                            | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_open                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_threads                                        | NO      | NO    |
| wait/synch/mutex/mysys/TMPDIR_mutex                                            | NO      | NO    |
| wait/synch/mutex/partition/Partition_share::auto_inc_mutex                     | NO      | NO    |
| wait/synch/mutex/sql/Ack_receiver::mutex                                       | NO      | NO    |
| wait/synch/mutex/sql/Cversion_lock                                             | NO      | NO    |
| wait/synch/mutex/sql/Delayed_insert::mutex                                     | NO      | NO    |
| wait/synch/mutex/sql/Event_scheduler::LOCK_scheduler_state                     | NO      | NO    |
| wait/synch/mutex/sql/gtid_waiting::LOCK_gtid_waiting                           | NO      | NO    |
| wait/synch/mutex/sql/hash_filo::lock                                           | NO      | NO    |
| wait/synch/mutex/sql/HA_DATA_PARTITION::LOCK_auto_inc                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_active_mi                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_after_binlog_sync                                    | NO      | NO    |
| wait/synch/mutex/sql/LOCK_audit_mask                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_binlog                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_binlog_state                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_commit_ordered                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_crypt                                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_create                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_insert                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_status                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_des_key_file                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_error_log                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_error_messages                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_event_queue                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_gdl                                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_index_stats                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_system_variables                              | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_table_stats                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_user_client_stats                             | NO      | NO    |
| wait/synch/mutex/sql/LOCK_item_func_sleep                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_load_client_plugin                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_manager                                              | NO      | NO    |
| wait/synch/mutex/sql/LOCK_parallel_entry                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_plugin                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_prepared_stmt_count                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_prepare_ordered                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_semi_sync_master_enabled                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_status                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_thread                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_thread_pool                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_server_started                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_slave_background                                     | NO      | NO    |
| wait/synch/mutex/sql/LOCK_slave_state                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_start_thread                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_stats                                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_status                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_system_variables_hash                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_table_cache                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_thread_cache                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_thread_id                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_unused_shares                                        | NO      | NO    |
| wait/synch/mutex/sql/LOCK_user_conn                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_uuid_short_generator                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_cluster_config                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_config_state                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_desync                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_donor_monitor                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_group_commit                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_gtid_wait_upto                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_joiner_monitor                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_ready                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_replaying                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_slave_threads                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_SR_pool                                        | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_SR_store                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_sst                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_sst_init                                       | NO      | NO    |
| wait/synch/mutex/sql/LOG::LOCK_log                                             | NO      | NO    |
| wait/synch/mutex/sql/Master_info::data_lock                                    | NO      | NO    |
| wait/synch/mutex/sql/Master_info::run_lock                                     | NO      | NO    |
| wait/synch/mutex/sql/Master_info::sleep_lock                                   | NO      | NO    |
| wait/synch/mutex/sql/Master_info::start_stop_lock                              | NO      | NO    |
| wait/synch/mutex/sql/MDL_wait::LOCK_wait_status                                | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_binlog_background_thread              | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_binlog_end_pos                        | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_index                                 | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_xid_list                              | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_RELAY_LOG::LOCK_binlog_end_pos                      | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_RELAY_LOG::LOCK_index                               | NO      | NO    |
| wait/synch/mutex/sql/PAGE::lock                                                | NO      | NO    |
| wait/synch/mutex/sql/Query_cache::structure_guard_mutex                        | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::data_lock                                 | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::log_space_lock                            | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::run_lock                                  | NO      | NO    |
| wait/synch/mutex/sql/Rpl_group_info::sleep_lock                                | NO      | NO    |
| wait/synch/mutex/sql/Slave_reporting_capability::err_lock                      | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_ha_data                                 | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_rotation                                | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_share                                   | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::tdc.LOCK_table_share                         | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_active                                  | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pending_checkpoint                      | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pool                                    | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_sync                                    | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_thd_data                                        | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_thd_kill                                        | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_wakeup_ready                                    | NO      | NO    |
| wait/synch/mutex/sql/tz_LOCK                                                   | NO      | NO    |
| wait/synch/mutex/sql/wait_for_commit::LOCK_wait_commit                         | NO      | NO    |
| wait/synch/mutex/sql/wsrep_sst_thread                                          | NO      | NO    |
| wait/synch/rwlock/aria/KEYINFO::root_lock                                      | NO      | NO    |
| wait/synch/rwlock/aria/SHARE::mmap_lock                                        | NO      | NO    |
| wait/synch/rwlock/aria/TRANSLOG_DESCRIPTOR::open_files_lock                    | NO      | NO    |
| wait/synch/rwlock/myisam/MYISAM_SHARE::key_root_lock                           | NO      | NO    |
| wait/synch/rwlock/myisam/MYISAM_SHARE::mmap_lock                               | NO      | NO    |
| wait/synch/rwlock/mysys/SAFE_HASH::mutex                                       | NO      | NO    |
| wait/synch/rwlock/proxy_proto/rwlock                                           | NO      | NO    |
| wait/synch/rwlock/sql/CRYPTO_dynlock_value::lock                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_all_status_vars                                     | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_dboptions                                           | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_grant                                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_SEQUENCE                                            | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_ssl_refresh                                         | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_system_variables_hash                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_sys_init_connect                                    | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_sys_init_slave                                      | NO      | NO    |
| wait/synch/rwlock/sql/LOGGER::LOCK_logger                                      | NO      | NO    |
| wait/synch/rwlock/sql/MDL_context::LOCK_waiting_for                            | NO      | NO    |
| wait/synch/rwlock/sql/MDL_lock::rwlock                                         | NO      | NO    |
| wait/synch/rwlock/sql/Query_cache_query::lock                                  | NO      | NO    |
| wait/synch/rwlock/sql/TABLE_SHARE::LOCK_stat_serial                            | NO      | NO    |
| wait/synch/rwlock/sql/THD_list::lock                                           | NO      | NO    |
| wait/synch/rwlock/sql/THR_LOCK_servers                                         | NO      | NO    |
| wait/synch/rwlock/sql/THR_LOCK_udf                                             | NO      | NO    |
| wait/synch/rwlock/sql/Vers_field_stats::lock                                   | NO      | NO    |
| wait/synch/sxlock/innodb/btr_search_latch                                      | NO      | NO    |
| wait/synch/sxlock/innodb/dict_operation_lock                                   | NO      | NO    |
| wait/synch/sxlock/innodb/fil_space_latch                                       | NO      | NO    |
| wait/synch/sxlock/innodb/fts_cache_init_rw_lock                                | NO      | NO    |
| wait/synch/sxlock/innodb/fts_cache_rw_lock                                     | NO      | NO    |
| wait/synch/sxlock/innodb/index_online_log                                      | NO      | NO    |
| wait/synch/sxlock/innodb/index_tree_rw_lock                                    | NO      | NO    |
| wait/synch/sxlock/innodb/trx_i_s_cache_lock                                    | NO      | NO    |
| wait/synch/sxlock/innodb/trx_purge_latch                                       | NO      | NO    |
+--------------------------------------------------------------------------------+---------+-------+
996 rows in set (0.005 sec)

1.1.2.9.2.1.64 Performance Schema setup_objects Table

Description

The setup_objects table determines whether objects are monitored by the performance schema or not. By default limited to 100 rows, this can be changed by setting the performance_schema_setup_objects_size system variable when the server starts.

It contains the following columns:

ColumnDescription
OBJECT_TYPEType of object to instrument, currently only . Currently, only TABLE', for base table.
OBJECT_SCHEMASchema containing the object, either the literal or % for any schema.
OBJECT_NAMEName of the instrumented object, either the literal or % for any object.
ENABLEDWhether the object's events are instrumented or not. Can be disabled, in which case monitoring is not enabled for those objects.
TIMEDWhether the object's events are timed or not. Can be modified.

When the Performance Schema looks for matches in the setup_objects, there may be more than one row matching, with different ENABLED and TIMED values. It looks for the most specific matches first, that is, it will first look for the specific database and table name combination, then the specific database, only then falling back to a wildcard for both.

Rows can be added or removed from the table, while for existing rows, only the TIMED and ENABLED columns can be updated. By default, all tables except those in the performance_schema, information_schema and mysql databases are instrumented.

1.1.2.9.2.1.65 Performance Schema setup_timers Table

Description

The setup_timers table shows the currently selected event timers.

It contains the following columns:

ColumnDescription
NAMEType of instrument the timer is used for.
TIMER_NAMETimer applying to the instrument type. Can be modified.

The TIMER_NAME value can be changed to choose a different timer, and can be any non-NULL value in the performance_timers.TIMER_NAME column.

If you modify the table, monitoring is immediately affected, and currently monitored events would use a combination of old and new timers, which is probably undesirable. It is best to reset the Performance Schema statistics if you make changes to this table.

Example

SELECT * FROM setup_timers;
+-----------+-------------+
| NAME      | TIMER_NAME  |
+-----------+-------------+
| idle      | MICROSECOND |
| wait      | CYCLE       |
| stage     | NANOSECOND  |
| statement | NANOSECOND  |
+-----------+-------------+

1.1.2.9.2.1.66 Performance Schema socket_instances Table

The socket_instances table lists active server connections, with each record being a Unix socket file or TCP/IP connection.

The socket_instances table contains the following columns:

ColumnDescription
EVENT_NAMENAME from the setup_instruments table, and the name of the wait/io/socket/* instrument that produced the event.
OBJECT_INSTANCE_BEGINMemory address of the object.
THREAD_IDThread identifier that the server assigns to each socket.
SOCKET_IDThe socket's internal file handle.
IPClient IP address. Blank for Unix socket file, otherwise an IPv4 or IPv6 address. Together with the PORT identifies the connection.
PORTTCP/IP port number, from 0 to 65535. Together with the IP identifies the connection.
STATESocket status, either IDLE if waiting to receive a request from a client, or ACTIVE

1.1.2.9.2.1.67 Performance Schema socket_summary_by_event_name Table

It aggregates timer and byte count statistics for all socket I/O operations by socket instrument.

ColumnDescription
EVENT_NAMESocket instrument.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including RECV, RECVFROM, and RECVMSG.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including SEND, SENDTO, and SENDMSG.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CONNECT, LISTEN, ACCEPT, CLOSE, and SHUTDOWN.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM socket_summary_by_event_name\G
*************************** 1. row ***************************
               EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
               COUNT_STAR: 0
           SUM_TIMER_WAIT: 0
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 0
           MAX_TIMER_WAIT: 0
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 0
           SUM_TIMER_MISC: 0
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 0
           MAX_TIMER_MISC: 0
*************************** 2. row ***************************
               EVENT_NAME: wait/io/socket/sql/server_unix_socket
               COUNT_STAR: 0
           SUM_TIMER_WAIT: 0
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 0
           MAX_TIMER_WAIT: 0
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 0
           SUM_TIMER_MISC: 0
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 0
           MAX_TIMER_MISC: 0
...

1.1.2.9.2.1.68 Performance Schema socket_summary_by_instance Table

It aggregates timer and byte count statistics for all socket I/O operations by socket instance.

ColumnDescription
EVENT_NAMESocket instrument.
OBJECT_INSTANCE_BEGINAddress in memory.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including RECV, RECVFROM, and RECVMSG.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including SEND, SENDTO, and SENDMSG.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CONNECT, LISTEN, ACCEPT, CLOSE, and SHUTDOWN.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

The corresponding row in the table is deleted when a connection terminates.

You can TRUNCATE the table, which will reset all counters to zero.

1.1.2.9.2.1.69 Performance Schema status_by_thread Table

MariaDB starting with 10.5.2

The session_status table was added in MariaDB 10.5.2.

The status_by_thread table contains status variable information about active foreground threads. The table does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
THREAD_IDThe thread identifier of the session in which the status variable is defined.
VARIABLE_NAMEStatus variable name.
VARIABLE_VALUEAggregated status variable value.

If TRUNCATE TABLE is run, will aggregate the status for all threads to the global status and account status, then reset the thread status. If account statistics are not collected but host and user status are, the session status is added to host and user status.

1.1.2.9.2.1.70 Performance Schema table_io_waits_summary_by_index_usage Table

The table_io_waits_summary_by_index_usage table records table I/O waits by index.

ColumnDescription
OBJECT_TYPETABLE in the case of all indexes.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
INDEX_NAMEIndex name, or PRIMARY for the primary index, NULL for no index (inserts are counted in this case).
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_FETCH columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_INSERT, x_UPDATE and x_DELETE columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_FETCHNumber of all fetch operations.
SUM_TIMER_FETCHTotal wait time of all fetch operations that are timed.
MIN_TIMER_FETCHMinimum wait time of all fetch operations that are timed.
AVG_TIMER_FETCHAverage wait time of all fetch operations that are timed.
MAX_TIMER_FETCHMaximum wait time of all fetch operations that are timed.
COUNT_INSERTNumber of all insert operations.
SUM_TIMER_INSERTTotal wait time of all insert operations that are timed.
MIN_TIMER_INSERTMinimum wait time of all insert operations that are timed.
AVG_TIMER_INSERTAverage wait time of all insert operations that are timed.
MAX_TIMER_INSERTMaximum wait time of all insert operations that are timed.
COUNT_UPDATENumber of all update operations.
SUM_TIMER_UPDATETotal wait time of all update operations that are timed.
MIN_TIMER_UPDATEMinimum wait time of all update operations that are timed.
AVG_TIMER_UPDATEAverage wait time of all update operations that are timed.
MAX_TIMER_UPDATEMaximum wait time of all update operations that are timed.
COUNT_DELETENumber of all delete operations.
SUM_TIMER_DELETETotal wait time of all delete operations that are timed.
MIN_TIMER_DELETEMinimum wait time of all delete operations that are timed.
AVG_TIMER_DELETEAverage wait time of all delete operations that are timed.
MAX_TIMER_DELETEMaximum wait time of all delete operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero. The table is also truncated if the table_io_waits_summary_by_table table is truncated.

If a table's index structure is changed, index statistics recorded in this table may also be reset.

1.1.2.9.2.1.71 Performance Schema table_io_waits_summary_by_table Table

The table_io_waits_summary_by_table table records table I/O waits by table.

ColumnDescription
OBJECT_TYPESince this table records waits by table, always set to TABLE.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_FETCH columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_INSERT, x_UPDATE and x_DELETE columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_FETCHNumber of all fetch operations.
SUM_TIMER_FETCHTotal wait time of all fetch operations that are timed.
MIN_TIMER_FETCHMinimum wait time of all fetch operations that are timed.
AVG_TIMER_FETCHAverage wait time of all fetch operations that are timed.
MAX_TIMER_FETCHMaximum wait time of all fetch operations that are timed.
COUNT_INSERTNumber of all insert operations.
SUM_TIMER_INSERTTotal wait time of all insert operations that are timed.
MIN_TIMER_INSERTMinimum wait time of all insert operations that are timed.
AVG_TIMER_INSERTAverage wait time of all insert operations that are timed.
MAX_TIMER_INSERTMaximum wait time of all insert operations that are timed.
COUNT_UPDATENumber of all update operations.
SUM_TIMER_UPDATETotal wait time of all update operations that are timed.
MIN_TIMER_UPDATEMinimum wait time of all update operations that are timed.
AVG_TIMER_UPDATEAverage wait time of all update operations that are timed.
MAX_TIMER_UPDATEMaximum wait time of all update operations that are timed.
COUNT_DELETENumber of all delete operations.
SUM_TIMER_DELETETotal wait time of all delete operations that are timed.
MIN_TIMER_DELETEMinimum wait time of all delete operations that are timed.
AVG_TIMER_DELETEAverage wait time of all delete operations that are timed.
MAX_TIMER_DELETEMaximum wait time of all delete operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero. Truncating this table will also truncate the table_io_waits_summary_by_index_usage table.

1.1.2.9.2.1.72 Performance Schema table_lock_waits_summary_by_table Table

The table_lock_waits_summary_by_table table records table lock waits by table.

ColumnDescription
OBJECT_TYPESince this table records waits by table, always set to TABLE.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_READ_NORMAL, x_READ_WITH_SHARED_LOCKS, x_READ_HIGH_PRIORITY and x_READ_NO_INSERT columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_WRITE_ALLOW_WRITE, x_WRITE_CONCURRENT_INSERT, x_WRITE_DELAYED, x_WRITE_LOW_PRIORITY and x_WRITE_NORMAL columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_READ_NORMALNumber of all internal read normal locks.
SUM_TIMER_READ_NORMALTotal wait time of all internal read normal locks that are timed.
MIN_TIMER_READ_NORMALMinimum wait time of all internal read normal locks that are timed.
AVG_TIMER_READ_NORMALAverage wait time of all internal read normal locks that are timed.
MAX_TIMER_READ_NORMALMaximum wait time of all internal read normal locks that are timed.
COUNT_READ_WITH_SHARED_LOCKSNumber of all internal read with shared locks.
SUM_TIMER_READ_WITH_SHARED_LOCKSTotal wait time of all internal read with shared locks that are timed.
MIN_TIMER_READ_WITH_SHARED_LOCKSMinimum wait time of all internal read with shared locks that are timed.
AVG_TIMER_READ_WITH_SHARED_LOCKSAverage wait time of all internal read with shared locks that are timed.
MAX_TIMER_READ_WITH_SHARED_LOCKSMaximum wait time of all internal read with shared locks that are timed.
COUNT_READ_HIGH_PRIORITYNumber of all internal read high priority locks.
SUM_TIMER_READ_HIGH_PRIORITYTotal wait time of all internal read high priority locks that are timed.
MIN_TIMER_READ_HIGH_PRIORITYMinimum wait time of all internal read high priority locks that are timed.
AVG_TIMER_READ_HIGH_PRIORITYAverage wait time of all internal read high priority locks that are timed.
MAX_TIMER_READ_HIGH_PRIORITYMaximum wait time of all internal read high priority locks that are timed.
COUNT_READ_NO_INSERTNumber of all internal read no insert locks.
SUM_TIMER_READ_NO_INSERTTotal wait time of all internal read no insert locks that are timed.
MIN_TIMER_READ_NO_INSERTMinimum wait time of all internal read no insert locks that are timed.
AVG_TIMER_READ_NO_INSERTAverage wait time of all internal read no insert locks that are timed.
MAX_TIMER_READ_NO_INSERTMaximum wait time of all internal read no insert locks that are timed.
COUNT_READ_EXTERNALNumber of all external read locks.
SUM_TIMER_READ_EXTERNALTotal wait time of all external read locks that are timed.
MIN_TIMER_READ_EXTERNALMinimum wait time of all external read locks that are timed.
AVG_TIMER_READ_EXTERNALAverage wait time of all external read locks that are timed.
MAX_TIMER_READ_EXTERNALMaximum wait time of all external read locks that are timed.
COUNT_WRITE_ALLOW_WRITENumber of all internal read normal locks.
SUM_TIMER_WRITE_ALLOW_WRITETotal wait time of all internal write allow write locks that are timed.
MIN_TIMER_WRITE_ALLOW_WRITEMinimum wait time of all internal write allow write locks that are timed.
AVG_TIMER_WRITE_ALLOW_WRITEAverage wait time of all internal write allow write locks that are timed.
MAX_TIMER_WRITE_ALLOW_WRITEMaximum wait time of all internal write allow write locks that are timed.
COUNT_WRITE_CONCURRENT_INSERTNumber of all internal concurrent insert write locks.
SUM_TIMER_WRITE_CONCURRENT_INSERTTotal wait time of all internal concurrent insert write locks that are timed.
MIN_TIMER_WRITE_CONCURRENT_INSERTMinimum wait time of all internal concurrent insert write locks that are timed.
AVG_TIMER_WRITE_CONCURRENT_INSERTAverage wait time of all internal concurrent insert write locks that are timed.
MAX_TIMER_WRITE_CONCURRENT_INSERTMaximum wait time of all internal concurrent insert write locks that are timed.
COUNT_WRITE_DELAYEDNumber of all internal write delayed locks.
SUM_TIMER_WRITE_DELAYEDTotal wait time of all internal write delayed locks that are timed.
MIN_TIMER_WRITE_DELAYEDMinimum wait time of all internal write delayed locks that are timed.
AVG_TIMER_WRITE_DELAYEDAverage wait time of all internal write delayed locks that are timed.
MAX_TIMER_WRITE_DELAYEDMaximum wait time of all internal write delayed locks that are timed.
COUNT_WRITE_LOW_PRIORITYNumber of all internal write low priority locks.
SUM_TIMER_WRITE_LOW_PRIORITYTotal wait time of all internal write low priority locks that are timed.
MIN_TIMER_WRITE_LOW_PRIORITYMinimum wait time of all internal write low priority locks that are timed.
AVG_TIMER_WRITE_LOW_PRIORITYAverage wait time of all internal write low priority locks that are timed.
MAX_TIMER_WRITE_LOW_PRIORITYMaximum wait time of all internal write low priority locks that are timed.
COUNT_WRITE_NORMALNumber of all internal write normal locks.
SUM_TIMER_WRITE_NORMALTotal wait time of all internal write normal locks that are timed.
MIN_TIMER_WRITE_NORMALMinimum wait time of all internal write normal locks that are timed.
AVG_TIMER_WRITE_NORMALAverage wait time of all internal write normal locks that are timed.
MAX_TIMER_WRITE_NORMALMaximum wait time of all internal write normal locks that are timed.
COUNT_WRITE_EXTERNALNumber of all external write locks.
SUM_TIMER_WRITE_EXTERNALTotal wait time of all external write locks that are timed.
MIN_TIMER_WRITE_EXTERNALMinimum wait time of all external write locks that are timed.
AVG_TIMER_WRITE_EXTERNALAverage wait time of all external write locks that are timed.
MAX_TIMER_WRITE_EXTERNALMaximum wait time of all external write locks that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

1.1.2.9.2.1.73 Performance Schema threads Table

Each server thread is represented as a row in the threads table.

The threads table contains the following columns:

ColumnDescriptionAdded
THREAD_IDA unique thread identifier.MariaDB 5.5
NAMEName associated with the server's thread instrumentation code, for example thread/sql/main for the server's main() function, and thread/sql/one_connection for a user connection.MariaDB 5.5
TYPEFOREGROUND or BACKGROUND, depending on the thread type. User connection threads are FOREGROUND, internal server threads are BACKGROUND.MariaDB 10.0
PROCESSLIST_IDThe PROCESSLIST.ID value for threads displayed in the INFORMATION_SCHEMA.PROCESSLIST table, or 0 for background threads. Also corresponds with the CONNECTION_ID() return value for the thread.MariaDB 5.5
PROCESSLIST_USERForeground thread user, or NULL for a background thread.MariaDB 10.0
PROCESSLIST_HOSTForeground thread host, or NULL for a background thread.MariaDB 10.0
PROCESSLIST_DBThread's default database, or NULL if none exists.MariaDB 10.0
PROCESSLIST_COMMANDType of command executed by the thread. These correspond to the the COM_xxx client/server protocol commands, and the Com_xxx status variables. See Thread Command Values.MariaDB 10.0
PROCESSLIST_TIMETime in seconds the thread has been in its current state.MariaDB 10.0
PROCESSLIST_STATEAction, event or state indicating what the thread is doing.MariaDB 10.0
PROCESSLIST_INFOStatement being executed by the thread, or NULL if a statement is not being executed. If a statement results in calling other statements, such as for a stored procedure, the innermost statement from the stored procedure is shown here.MariaDB 10.0
PARENT_THREAD_IDTHREAD_ID of the parent thread, if any. Subthreads can for example be spawned as a result of INSERT DELAYED statements.MariaDB 10.0
ROLEUnused.MariaDB 10.0
INSTRUMENTEDYES or NO for Whether the thread is instrumented or not. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES.MariaDB 10.0
HISTORYYES or NO for Whether to log historical events for the thread. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES.MariaDB 10.5
CONNECTION_TYPEThe protocol used to establish the connection, or NULL for background threads.MariaDB 10.5
THREAD_OS_IDThe thread or task identifier as defined by the underlying operating system, if there is one.MariaDB 10.5

Example

SELECT * FROM performance_schema.threads\G;
*************************** 1. row ***************************
          THREAD_ID: 1
               NAME: thread/sql/main
               TYPE: BACKGROUND
     PROCESSLIST_ID: NULL
   PROCESSLIST_USER: NULL
   PROCESSLIST_HOST: NULL
     PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: NULL
   PROCESSLIST_TIME: 215859
  PROCESSLIST_STATE: Table lock
   PROCESSLIST_INFO: INTERNAL DDL LOG RECOVER IN PROGRESS
   PARENT_THREAD_ID: NULL
               ROLE: NULL
       INSTRUMENTED: YES
...
*************************** 21. row ***************************
          THREAD_ID: 64
               NAME: thread/sql/one_connection
               TYPE: FOREGROUND
     PROCESSLIST_ID: 44
   PROCESSLIST_USER: root
   PROCESSLIST_HOST: localhost
     PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: Query
   PROCESSLIST_TIME: 0
  PROCESSLIST_STATE: Sending data
   PROCESSLIST_INFO: SELECT * FROM performance_schema.threads
   PARENT_THREAD_ID: NULL
               ROLE: NULL
       INSTRUMENTED: YES

1.1.2.9.2.1.74 Performance Schema users Table

Description

Each user that connects to the server is stored as a row in the users table, along with current and total connections.

The table size is determined at startup by the value of the performance_schema_users_size system variable. If this is set to 0, user statistics will be disabled.

ColumnDescription
USERThe connection's client user name for the connection, or NULL if an internal thread.
CURRENT_CONNECTIONSCurrent connections for the user.
TOTAL_CONNECTIONSTotal connections for the user.

Example

SELECT * FROM performance_schema.users;
+------------------+---------------------+-------------------+
| USER             | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+---------------------+-------------------+
| debian-sys-maint |                   0 |                35 |
| NULL             |                  20 |                23 |
| root             |                   1 |                 2 |
+------------------+---------------------+-------------------+

1.1.2.9.2.2 Performance Schema Overview

The Performance Schema is a feature for monitoring server performance.


Introduction

It is implemented as a storage engine, and so will appear in the list of storage engines available.

SHOW ENGINES;
+--------------------+---------+----------------------------------+--------------+------+------------+
| Engine             | Support | Comment                          | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------+--------------+------+------------+
| ...                |         |                                  |              |      |            |
| PERFORMANCE_SCHEMA | YES     | Performance Schema               | NO           | NO   | NO         |
| ...                |         |                                  |              |      |            |
+--------------------+---------+----------------------------------+--------------+------+------------+

However, performance_schema is not a regular storage engine for storing data, it's a mechanism for implementing the Performance Schema feature.

The storage engine contains a database called performance_schema, which in turn consists of a number of tables that can be queried with regular SQL statements, returning specific performance information.

USE performance_schema
SHOW TABLES;
+----------------------------------------------------+
| Tables_in_performance_schema                       |
+----------------------------------------------------+
| accounts                                           |
...
| users                                              |
+----------------------------------------------------+
80 rows in set (0.00 sec)

See List of Performance Schema Tables for a full list and links to detailed descriptions of each table. From MariaDB 10.5, there are 80 Performance Schema tables, while until MariaDB 10.4, there are 52.

Activating the Performance Schema

The performance schema is disabled by default for performance reasons. You can check its current status by looking at the value of the performance_schema system variable.

SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

The performance schema cannot be activated at runtime - it must be set when the server starts by adding the following line in your my.cnf configuration file.

performance_schema=ON

Until MariaDB 10.4, all memory used by the Performance Schema is allocated at startup. From MariaDB 10.5, some memory is allocated dynamically, depending on load, number of connections, number of tables open etc.

Enabling the Performance Schema

You need to set up all consumers (starting collection of data) and instrumentations (what to collect):

UPDATE performance_schema.setup_consumers SET ENABLED = 'YES';
UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES';

You can decide what to enable/disable with WHERE NAME like "%what_to_enable"; You can disable instrumentations by setting ENABLED to "NO".

You can also do this in your my.cnf file. The following enables all instrumentation of all stages (computation units) in MariaDB:

[mysqld]
performance_schema=ON
performance-schema-instrument='stage/%=ON'
performance-schema-consumer-events-stages-current=ON
performance-schema-consumer-events-stages-history=ON
performance-schema-consumer-events-stages-history-long=ON

Listing Performance Schema Variables

SHOW VARIABLES LIKE "perf%";
+--------------------------------------------------------+-------+
| Variable_name                                          | Value |
+--------------------------------------------------------+-------+
| performance_schema                                     | ON    |
...
| performance_schema_users_size                          | 100   |
+--------------------------------------------------------+-------+

See Performance Schema System Variables for a full list of available system variables.

Note that the "consumer" events are not shown on this list, as they are only available as options, not as system variables, and they can only be enabled at startup.

Column Comments

MariaDB starting with 10.7.1

From MariaDB 10.7.1, comments have been added to table columns in the Performance Schema. These can be viewed with, for example:

SELECT column_name, column_comment FROM information_schema.columns 
  WHERE table_schema='performance_schema' AND table_name='file_instances';
...
*************************** 2. row ***************************
   column_name: EVENT_NAME
column_comment: Instrument name associated with the file.
*************************** 3. row ***************************
   column_name: OPEN_COUNT
column_comment: Open handles on the file. A value of greater than zero means 
                that the file is currently open.
...

See Also

1.1.2.9.2.3 Performance Schema Status Variables

This page documents status variables related to the Performance Schema. See Server Status Variables for a complete list of status variables that can be viewed with SHOW STATUS.

See also the Full list of MariaDB options, system and status variables.

Performance_schema_accounts_lost

  • Description: Number of times a row could not be added to the performance schema accounts table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_cond_classes_lost

  • Description: Number of condition instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_cond_instances_lost

  • Description: Number of instances a condition object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_digest_lost

  • Description: The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_classes_lost

  • Description: Number of file instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_handles_lost

  • Description: Number of instances a file object could not be opened. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_instances_lost

  • Description: Number of instances a file object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_hosts_lost

  • Description: Number of times a row could not be added to the performance schema hosts table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_index_stat_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_locker_lost

  • Description: Number of events not recorded, due to either being recursive, or having a deeper nested events stack than the implementation limit. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_memory_classes_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_metadata_lock_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_mutex_classes_lost

  • Description: Number of mutual exclusion instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_mutex_instances_lost

  • Description: Number of instances a mutual exclusion object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_nested_statement_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_prepared_statements_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_program_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_rwlock_classes_lost

  • Description: Number of read/write lock instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_rwlock_instances_lost

  • Description: Number of instances a read/write lock object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_session_connect_attrs_lost

  • Description: Number of connections for which connection attribute truncation has occurred. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_socket_classes_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_socket_instances_lost

  • Description: Number of instances a socket object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_stage_classes_lost

  • Description: Number of stage event instruments that could not be loaded. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_statement_classes_lost

  • Description: Number of statement instruments that could not be loaded. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_handles_lost

  • Description: Number of instances a table object could not be opened. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_instances_lost

  • Description: Number of instances a table object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_lock_stat_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_thread_classes_lost

  • Description: Number of thread instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_thread_instances_lost

  • Description: Number of instances thread object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_users_lost

  • Description: Number of times a row could not be added to the performance schema users table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

1.1.2.9.2.4 Performance Schema System Variables

Contents

  1. performance_schema
  2. performance_schema_accounts_size
  3. performance_schema_digests_size
  4. performance_schema_events_stages_history_long_size
  5. performance_schema_events_stages_history_size
  6. performance_schema_events_statements_history_long_size
  7. performance_schema_events_statements_history_size
  8. performance_schema_events_transactions_history_long_size
  9. performance_schema_events_transactions_history_size
  10. performance_schema_events_waits_history_long_size
  11. performance_schema_events_waits_history_size
  12. performance_schema_hosts_size
  13. performance_schema_max_cond_classes
  14. performance_schema_max_cond_instances
  15. performance_schema_max_digest_length
  16. performance_schema_max_file_classes
  17. performance_schema_max_file_handles
  18. performance_schema_max_file_instances
  19. performance_schema_max_index_stat
  20. performance_schema_max_memory_classes
  21. performance_schema_max_metadata_locks
  22. performance_schema_max_mutex_classes
  23. performance_schema_max_mutex_instances
  24. performance_schema_max_prepared_statement_instances
  25. performance_schema_max_program_instances
  26. performance_schema_max_rwlock_classes
  27. performance_schema_max_rwlock_instances
  28. performance_schema_max_socket_classes
  29. performance_schema_max_socket_instances
  30. performance_schema_max_sql_text_length
  31. performance_schema_max_stage_classes
  32. performance_schema_max_statement_classes
  33. performance_schema_max_statement_stack
  34. performance_schema_max_table_handles
  35. performance_schema_max_table_instances
  36. performance_schema_max_table_lock_stat
  37. performance_schema_max_thread_classes
  38. performance_schema_max_thread_instances
  39. performance_schema_session_connect_attrs_size
  40. performance_schema_setup_actors_size
  41. performance_schema_setup_objects_size
  42. performance_schema_users_size

The following variables are used with MariaDB's Performance Schema. See Performance Schema Options for Performance Schema options that are not system variables. See Server System Variables for a complete list of system variables and instructions on setting them.

See also the Full list of MariaDB options, system and status variables.

performance_schema

  • Description: If set to 1 (0 is default), enables the Performance Schema
  • Commandline: --performance-schema=#
  • Scope: Global
  • Dynamic: No
  • Data Type: boolean
  • Default Value: OFF

performance_schema_accounts_size

  • Description: Maximum number of rows in the performance_schema.accounts table. If set to 0, the Performance Schema will not store statistics in the accounts table. Use -1 (the default) for automated sizing.
  • Commandline: --performance-schema-accounts-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_digests_size

  • Description: Maximum number of rows that can be stored in the events_statements_summary_by_digest table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-digests-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 200

performance_schema_events_stages_history_long_size

  • Description: Number of rows in the events_stages_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-stages-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_stages_history_size

  • Description: Number of rows per thread in the events_stages_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-stages-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_events_statements_history_long_size

  • Description: Number of rows in the events_statements_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-statements-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_statements_history_size

  • Description: Number of rows per thread in the events_statements_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-statements-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_events_transactions_history_long_size

  • Description: Number of rows in events_transactions_history_long table. Use 0 to disable, -1 for automated sizing.
  • Commandline: --performance-schema-events-transactions-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_events_transactions_history_size

  • Description:Number of rows per thread in events_transactions_history. Use 0 to disable, -1 for automated sizing.
  • Commandline: --performance-schema-events-transactions-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024
  • Introduced: MariaDB 10.5.2

performance_schema_events_waits_history_long_size

  • Description: Number of rows contained in the events_waits_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-waits-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_waits_history_size

  • Description: Number of rows per thread contained in the events_waits_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-waits-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_hosts_size

  • Description: Number of rows stored in the hosts table. If set to zero, no connection statistics are kept for the hosts table. -1 (the default) for automated sizing.
  • Commandline: --performance-schema-hosts-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_cond_classes

  • Description: Specifies the maximum number of condition instruments.
  • Commandline: --performance-schema-max-cond-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 90 (>= MariaDB 10.5.1), 80 (<= MariaDB 10.5.0)
  • Range: 0 to 256

performance_schema_max_cond_instances

  • Description: Specifies the maximum number of instrumented condition objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-cond-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_digest_length

  • Description: Maximum length considered for digest text, when stored in performance_schema tables.
  • Commandline: --performance-schema-max-digest-length=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 1024
  • Range: 0 to 1048576

performance_schema_max_file_classes

  • Description: Specifies the maximum number of file instruments.
  • Commandline: --performance-schema-max-file-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:80 (>= MariaDB 10.5.2), 50 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_file_handles

  • Description: Specifies the maximum number of opened file objects. Should always be higher than open_files_limit.
  • Commandline: --performance-schema-max-file-handles=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 32768
  • Range: -1 to 32768

performance_schema_max_file_instances

  • Description: Specifies the maximum number of instrumented file objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-file-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_index_stat

  • Description: Maximum number of index statistics for instrumented tables. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-index-stat=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_memory_classes

  • Description: Maximum number of memory pool instruments.
  • Commandline: --performance-schema-max-memory-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 320
  • Range: 0 to 1024
  • Introduced: MariaDB 10.5.2

performance_schema_max_metadata_locks

  • Description: Maximum number of Performance Schema metadata locks. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-metadata-locks=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 104857600
  • Introduced: MariaDB 10.5.2

performance_schema_max_mutex_classes

  • Description: Specifies the maximum number of mutex instruments.
  • Commandline: --performance-schema-max-mutex-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 210 (>= MariaDB 10.5.2), 200 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_mutex_instances

  • Description: Specifies the maximum number of instrumented mutex instances. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-mutex-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 104857600

performance_schema_max_prepared_statement_instances

  • Description: Maximum number of instrumented prepared statements. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-prepared-statement-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_program_instances

  • Description: Maximum number of instrumented programs. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-program-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_rwlock_classes

  • Description: Specifies the maximum number of rwlock instruments.
  • Commandline: --performance-schema-max-rwlock-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 50 (>= MariaDB 10.5.2), 40 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_rwlock_instances

  • Description: Specifies the maximum number of instrumented rwlock objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-rwlock-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 104857600

performance_schema_max_socket_classes

  • Description: Specifies the maximum number of socket instruments.
  • Commandline: --performance-schema-max-socket-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 10
  • Range: 0 to 256

performance_schema_max_socket_instances

  • Description: Specifies the maximum number of instrumented socket objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-socket-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_max_sql_text_length

  • Description: Maximum length of displayed sql text.
  • Commandline: --performance-schema-max-sql-text-length=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 1024
  • Range: 0 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_stage_classes

  • Description: Specifies the maximum number of stage instruments.
  • Commandline: --performance-schema-max-stage-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 160 (>= MariaDB 10.3.3), 150 (<= MariaDB 10.3.2)
  • Range: 0 to 256

performance_schema_max_statement_classes

  • Description: Specifies the maximum number of statement instruments. Automatically calculated at server build based on the number of available statements. Should be left as either autosized or disabled, as changing to any positive value has no benefit and will most likely allocate unnecessary memory. Setting to zero disables all statement instrumentation, and no memory will be allocated for this purpose.
  • Commandline: --performance-schema-max-statement-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: Autosized (see description)
  • Range: 0 to 256

performance_schema_max_statement_stack

  • Description: Number of rows per thread in EVENTS_STATEMENTS_CURRENT.
  • Commandline: --performance-schema-max-statement-stack=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 10
  • Range: 1 to 256
  • Introduced: MariaDB 10.5.2

performance_schema_max_table_handles

  • Description: Specifies the maximum number of opened table objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-table-handles=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_table_instances

  • Description: Specifies the maximum number of instrumented table objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-table-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_max_table_lock_stat

  • Description: Maximum number of lock statistics for instrumented tables. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-table-lock-stat=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_thread_classes

  • Description: Specifies the maximum number of thread instruments.
  • Commandline: --performance-schema-max-thread-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 50
  • Range: 0 to 256

performance_schema_max_thread_instances

  • Description: Specifies how many of the running server threads (see max_connections and max_delayed_threads) can be instrumented. Should be greater than the sum of max_connections and max_delayed_threads. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-thread-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_session_connect_attrs_size

  • Description: Per thread preallocated memory for holding connection attribute strings. Incremented if the strings are larger than the reserved space. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-session-connect-attrs-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_setup_actors_size


performance_schema_setup_objects_size


performance_schema_users_size

  • Description: Number of rows in the performance_schema.users table. If set to 0, the Performance Schema will not store connection statistics in the users table. -1 (the default) for automated sizing.
  • Commandline: --performance-schema-users-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

1.1.2.9.2.5 Performance Schema Digests

The Performance Schema digest is a normalized form of a statement, with the specific data values removed. It allows statistics to be gathered for similar kinds of statements.

For example:

SELECT * FROM customer WHERE age < 20
SELECT * FROM customer WHERE age < 30

With the data values removed, both of these statements normalize to:

SELECT * FROM customer WHERE age < ?

which is the digest text. The digest text is then MD5 hashed, resulting in a digest. For example:

DIGEST_TEXT: SELECT * FROM `performance_schema` . `users`
DIGEST: 0f70cec4015f2a346df4ac0e9475d9f1

By contrast, the following two statements would not have the same digest as, while the data values are the same, they call upon different tables.

SELECT * FROM customer1 WHERE age < 20
SELECT * FROM customer2 WHERE age < 20

The digest text is limited to 1024 bytes. Queries exceeding this limit are truncated with '...', meaning that long queries that would otherwise have different digests may share the same digest.

Digest information is used in a number of performance scheme tables. These include

1.1.2.9.2.6 PERFORMANCE_SCHEMA Storage Engine

If you run SHOW ENGINES, you'll see the following storage engine listed.

SHOW ENGINES\G
...
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
...

The PERFORMANCE_SCHEMA is not a regular storage engine for storing data, it's a mechanism for implementing the Performance Schema feature.

The SHOW ENGINE PERFORMANCE_SCHEMA STATUS statement is also available, which shows how much memory is used by the tables and internal buffers.

See Performance Schema for more details.

1.1.2.9.3 The mysql Database Tables

AREA

A synonym for ST_AREA.

CENTROID

A synonym for ST_CENTROID.

ExteriorRing

A synonym for ST_ExteriorRing.

InteriorRingN

A synonym for ST_InteriorRingN.

NumInteriorRings

A synonym for ST_NumInteriorRings.

ST_AREA

Syntax

ST_Area(poly)
Area(poly)

Description

Returns as a double-precision number the area of the Polygon value poly, as measured in its spatial reference system.

ST_Area() and Area() are synonyms.

Examples

SET @poly = 'Polygon((0 0,0 3,3 0,0 0),(1 1,1 2,2 1,1 1))';

SELECT Area(GeomFromText(@poly));
+---------------------------+
| Area(GeomFromText(@poly)) |
+---------------------------+
|                         4 |
+---------------------------+

ST_CENTROID

Syntax

ST_Centroid(mpoly)
Centroid(mpoly)

Description

Returns a point reflecting the mathematical centroid (geometric center) for the MultiPolygon mpoly. The resulting point will not necessarily be on the MultiPolygon.

ST_Centroid() and Centroid() are synonyms.

Examples

SET @poly = ST_GeomFromText('POLYGON((0 0,20 0,20 20,0 20,0 0))');
SELECT ST_AsText(ST_Centroid(@poly)) AS center;
+--------------+
| center       |
+--------------+
| POINT(10 10) |
+--------------+

ST_ExteriorRing

Syntax

ST_ExteriorRing(poly)
ExteriorRing(poly)

Description

Returns the exterior ring of the Polygon value poly as a LineString.

ST_ExteriorRing() and ExteriorRing() are synonyms.

Examples

SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';

SELECT AsText(ExteriorRing(GeomFromText(@poly)));
+-------------------------------------------+
| AsText(ExteriorRing(GeomFromText(@poly))) |
+-------------------------------------------+
| LINESTRING(0 0,0 3,3 3,3 0,0 0)           |
+-------------------------------------------+

ST_InteriorRingN

Syntax

ST_InteriorRingN(poly,N)
InteriorRingN(poly,N)

Description

Returns the N-th interior ring for the Polygon value poly as a LineString. Rings are numbered beginning with 1.

ST_InteriorRingN() and InteriorRingN() are synonyms.

Examples

SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';

SELECT AsText(InteriorRingN(GeomFromText(@poly),1));
+----------------------------------------------+
| AsText(InteriorRingN(GeomFromText(@poly),1)) |
+----------------------------------------------+
| LINESTRING(1 1,1 2,2 2,2 1,1 1)              |
+----------------------------------------------+

ST_NumInteriorRings

Syntax

ST_NumInteriorRings(poly)
NumInteriorRings(poly)

Description

Returns an integer containing the number of interior rings in the Polygon value poly.

Note that according the the OpenGIS standard, a POLYGON should have exactly one ExteriorRing and all other rings should lie within that ExteriorRing and thus be the InteriorRings. Practically, however, some systems, including MariaDB's, permit polygons to have several 'ExteriorRings'. In the case of there being multiple, non-overlapping exterior rings ST_NumInteriorRings() will return 1.

ST_NumInteriorRings() and NumInteriorRings() are synonyms.

Examples

SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';

SELECT NumInteriorRings(GeomFromText(@poly));
+---------------------------------------+
| NumInteriorRings(GeomFromText(@poly)) |
+---------------------------------------+
|                                     1 |
+---------------------------------------+

Non-overlapping 'polygon':

SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10 0,10 10,0 10,0 0),
  (-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings;
+------------------+
| NumInteriorRings |
+------------------+
|                1 |
+------------------+

WKT Definition

Description

The Well-Known Text (WKT) representation of Geometry is designed to exchange geometry data in ASCII form. Examples of the basic geometry types include:

See Also

AsText

A synonym for ST_AsText().

AsWKT

A synonym for ST_AsText().

GeomCollFromText

A synonym for ST_GeomCollFromText.

GeometryCollectionFromText

A synonym for ST_GeomCollFromText.

GeometryFromText

A synonym for ST_GeomFromText.

GeomFromText

A synonym for ST_GeomFromText.

LineFromText

A synonym for ST_LineFromText.

LineStringFromText

A synonym for ST_LineFromText.

MLineFromText

Syntax

MLineFromText(wkt[,srid])
MultiLineStringFromText(wkt[,srid])

Description

Constructs a MULTILINESTRING value using its WKT representation and SRID.

MLineFromText() and MultiLineStringFromText() are synonyms.

Examples

CREATE TABLE gis_multi_line (g MULTILINESTRING);
SHOW FIELDS FROM gis_multi_line;
INSERT INTO gis_multi_line VALUES
    (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')),
    (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
    (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21, 7))))));

MPointFromText

Syntax

MPointFromText(wkt[,srid])
MultiPointFromText(wkt[,srid])

Description

Constructs a MULTIPOINT value using its WKT representation and SRID.

MPointFromText() and MultiPointFromText() are synonyms.

Examples

CREATE TABLE gis_multi_point (g MULTIPOINT);
SHOW FIELDS FROM gis_multi_point;
INSERT INTO gis_multi_point VALUES
    (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')),
    (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
    (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10)))));

MPolyFromText

Syntax

MPolyFromText(wkt[,srid])
MultiPolygonFromText(wkt[,srid])

Description

Constructs a MULTIPOLYGON value using its WKT representation and SRID.

MPolyFromText() and MultiPolygonFromText() are synonyms.

Examples

CREATE TABLE gis_multi_polygon  (g MULTIPOLYGON);
SHOW FIELDS FROM gis_multi_polygon;
INSERT INTO gis_multi_polygon VALUES
    (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));

MultiLineStringFromText

A synonym for MLineFromText.

MultiPointFromText

A synonym for MPointFromText.

MultiPolygonFromText

A synonym for MPolyFromText.

PointFromText

A synonym for ST_PointFromText.

PolyFromText

A synonym for ST_PolyFromText.

PolygonFromText

A synonym for ST_PolyFromText.

ST_AsText

Syntax

ST_AsText(g)
AsText(g)
ST_AsWKT(g)
AsWKT(g)

Description

Converts a value in internal geometry format to its WKT representation and returns the string result.

ST_AsText(), AsText(), ST_AsWKT() and AsWKT() are all synonyms.

Examples

SET @g = 'LineString(1 1,4 4,6 6)';

SELECT ST_AsText(ST_GeomFromText(@g));
+--------------------------------+
| ST_AsText(ST_GeomFromText(@g)) |
+--------------------------------+
| LINESTRING(1 1,4 4,6 6)        |
+--------------------------------+

ST_ASWKT

A synonym for ST_ASTEXT().

ST_GeomCollFromText

Syntax

ST_GeomCollFromText(wkt[,srid])
ST_GeometryCollectionFromText(wkt[,srid])
GeomCollFromText(wkt[,srid])
GeometryCollectionFromText(wkt[,srid])

Description

Constructs a GEOMETRYCOLLECTION value using its WKT representation and SRID.

ST_GeomCollFromText(), ST_GeometryCollectionFromText(), GeomCollFromText() and GeometryCollectionFromText() are all synonyms.

Example

CREATE TABLE gis_geometrycollection  (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
    (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')),
    (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))),
    (GeomFromText('GeometryCollection()')),
    (GeomFromText('GeometryCollection EMPTY'));

ST_GeometryCollectionFromText

A synonym for ST_GeomCollFromText.

ST_GeometryFromText

A synonym for ST_GeomFromText.

ST_GeomFromText

Syntax

ST_GeomFromText(wkt[,srid])
ST_GeometryFromText(wkt[,srid])
GeomFromText(wkt[,srid])
GeometryFromText(wkt[,srid])

Description

Constructs a geometry value of any type using its WKT representation and SRID.

GeomFromText(), GeometryFromText(), ST_GeomFromText() and ST_GeometryFromText() are all synonyms.

Example

SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))');

ST_LineFromText

Syntax

ST_LineFromText(wkt[,srid])
ST_LineStringFromText(wkt[,srid])
LineFromText(wkt[,srid])
LineStringFromText(wkt[,srid])

Description

Constructs a LINESTRING value using its WKT representation and SRID.

ST_LineFromText(), ST_LineStringFromText(), ST_LineFromText() and ST_LineStringFromText() are all synonyms.

Examples

CREATE TABLE gis_line  (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
    (LineFromText('LINESTRING(0 0,0 10,10 0)')),
    (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')),
    (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10)))));

ST_LineStringFromText

A synonym for ST_LineFromText.

ST_PointFromText

Syntax

ST_PointFromText(wkt[,srid])
PointFromText(wkt[,srid])

Description

Constructs a POINT value using its WKT representation and SRID.

ST_PointFromText() and PointFromText() are synonyms.

Examples

CREATE TABLE gis_point  (g POINT);
SHOW FIELDS FROM gis_point;
INSERT INTO gis_point VALUES
    (PointFromText('POINT(10 10)')),
    (PointFromText('POINT(20 10)')),
    (PointFromText('POINT(20 20)')),
    (PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));

ST_PolyFromText

Syntax

ST_PolyFromText(wkt[,srid])
ST_PolygonFromText(wkt[,srid])
PolyFromText(wkt[,srid])
PolygonFromText(wkt[,srid])

Description

Constructs a POLYGON value using its WKT representation and SRID.

ST_PolyFromText(), ST_PolygonFromText(), PolyFromText() and ST_PolygonFromText() are all synonyms.

Examples

CREATE TABLE gis_polygon   (g POLYGON);
INSERT INTO gis_polygon VALUES
    (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))'));

ST_PolygonFromText

A synonym for ST_PolyFromText.

Addition Operator (+)

Syntax

+

Description

Addition.

If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer.

For real or string operands, the operand with the highest precision determines the result precision.

Examples

SELECT 3+5;
+-----+
| 3+5 |
+-----+
|   8 |
+-----+

See Also

Subtraction Operator (-)

Syntax

-

Description

Subtraction. The operator is also used as the unary minus for changing sign.

If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer, unless the NO_UNSIGNED_SUBTRACTION SQL_MODE is enabled, in which case the result is always signed.

For real or string operands, the operand with the highest precision determines the result precision.

Examples

SELECT 96-9;
+------+
| 96-9 |
+------+
|   87 |
+------+

SELECT 15-17;
+-------+
| 15-17 |
+-------+
|    -2 |
+-------+

SELECT 3.66 + 1.333;
+--------------+
| 3.66 + 1.333 |
+--------------+
|        4.993 |
+--------------+

Unary minus:

 SELECT - (3+5);
+---------+
| - (3+5) |
+---------+
|      -8 |
+---------+

See Also

Division Operator (/)

Syntax

/

Description

Division operator. Dividing by zero will return NULL. By default, returns four digits after the decimal. This is determined by the server system variable div_precision_increment which by default is four. It can be set from 0 to 30.

Dividing by zero returns NULL. If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used (the default since MariaDB 10.2.4), a division by zero also produces a warning.

Examples

SELECT 4/5;
+--------+
| 4/5    |
+--------+
| 0.8000 |
+--------+

SELECT 300/(2-2);
+-----------+
| 300/(2-2) |
+-----------+
|      NULL |
+-----------+

SELECT 300/7;
+---------+
| 300/7   |
+---------+
| 42.8571 |
+---------+

Changing div_precision_increment for the session from the default of four to six:

SET div_precision_increment = 6;

SELECT 300/7;
+-----------+
| 300/7     |
+-----------+
| 42.857143 |
+-----------+

SELECT 300/7;
+-----------+
| 300/7     |
+-----------+
| 42.857143 |
+-----------+

See Also

Multiplication Operator (*)

Syntax

*

Description

Multiplication operator.

Examples

SELECT 7*6;
+-----+
| 7*6 |
+-----+
|  42 |
+-----+

SELECT 1234567890*9876543210;
+-----------------------+
| 1234567890*9876543210 |
+-----------------------+
|  -6253480962446024716 |
+-----------------------+

SELECT 18014398509481984*18014398509481984.0;
+---------------------------------------+
| 18014398509481984*18014398509481984.0 |
+---------------------------------------+
|   324518553658426726783156020576256.0 |
+---------------------------------------+

SELECT 18014398509481984*18014398509481984;
+-------------------------------------+
| 18014398509481984*18014398509481984 |
+-------------------------------------+
|                                   0 |
+-------------------------------------+

See Also

Modulo Operator (%)

Syntax

N % M

Description

Modulo operator. Returns the remainder of N divided by M. See also MOD.

Examples

SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
|        42 |
+-----------+

DIV

Syntax

DIV

Description

Integer division. Similar to FLOOR(), but is safe with BIGINT values. Incorrect results may occur for non-integer operands that exceed BIGINT range.

If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, a division by zero produces an error. Otherwise, it returns NULL.

The remainder of a division can be obtained using the MOD operator.

Examples

SELECT 300 DIV 7;
+-----------+
| 300 DIV 7 |
+-----------+
|        42 |
+-----------+

SELECT 300 DIV 0;
+-----------+
| 300 DIV 0 |
+-----------+
|      NULL |
+-----------+

ABS

Syntax

ABS(X)

Description

Returns the absolute (non-negative) value of X. If X is not a number, it is converted to a numeric type.

Examples

SELECT ABS(42);
+---------+
| ABS(42) |
+---------+
|      42 |
+---------+

SELECT ABS(-42);
+----------+
| ABS(-42) |
+----------+
|       42 |
+----------+

SELECT ABS(DATE '1994-01-01');
+------------------------+
| ABS(DATE '1994-01-01') |
+------------------------+
|               19940101 |
+------------------------+

See Also

ACOS

Syntax

ACOS(X)

Description

Returns the arc cosine of X, that is, the value whose cosine is X. Returns NULL if X is not in the range -1 to 1.

Examples

SELECT ACOS(1);
+---------+
| ACOS(1) |
+---------+
|       0 |
+---------+

SELECT ACOS(1.0001);
+--------------+
| ACOS(1.0001) |
+--------------+
|         NULL |
+--------------+

SELECT ACOS(0);
+-----------------+
| ACOS(0)         |
+-----------------+
| 1.5707963267949 |
+-----------------+

SELECT ACOS(0.234);
+------------------+
| ACOS(0.234)      |
+------------------+
| 1.33460644244679 |
+------------------+

ASIN

Syntax

ASIN(X)

Description

Returns the arc sine of X, that is, the value whose sine is X. Returns NULL if X is not in the range -1 to 1.

Examples

SELECT ASIN(0.2);
+--------------------+
| ASIN(0.2)          |
+--------------------+
| 0.2013579207903308 |
+--------------------+

SELECT ASIN('foo');
+-------------+
| ASIN('foo') |
+-------------+
|           0 |
+-------------+

SHOW WARNINGS;
+---------+------+-----------------------------------------+
| Level   | Code | Message                                 |
+---------+------+-----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'foo' |
+---------+------+-----------------------------------------+

ATAN

Syntax

ATAN(X)

Description

Returns the arc tangent of X, that is, the value whose tangent is X.

Examples

SELECT ATAN(2);
+--------------------+
| ATAN(2)            |
+--------------------+
| 1.1071487177940904 |
+--------------------+

SELECT ATAN(-2);
+---------------------+
| ATAN(-2)            |
+---------------------+
| -1.1071487177940904 |
+---------------------+

ATAN2

Syntax

ATAN(Y,X), ATAN2(Y,X)

Description

Returns the arc tangent of the two variables X and Y. It is similar to calculating the arc tangent of Y / X, except that the signs of both arguments are used to determine the quadrant of the result.

Examples

SELECT ATAN(-2,2);
+---------------------+
| ATAN(-2,2)          |
+---------------------+
| -0.7853981633974483 |
+---------------------+

SELECT ATAN2(PI(),0);
+--------------------+
| ATAN2(PI(),0)      |
+--------------------+
| 1.5707963267948966 |
+--------------------+

CEIL

Syntax

CEIL(X)

Description

CEIL() is a synonym for CEILING().

CEILING

Syntax

CEILING(X)

Description

Returns the smallest integer value not less than X.

Examples

SELECT CEILING(1.23);
+---------------+
| CEILING(1.23) |
+---------------+
|             2 |
+---------------+

SELECT CEILING(-1.23);
+----------------+
| CEILING(-1.23) |
+----------------+
|             -1 |
+----------------+

CONV

Syntax

CONV(N,from_base,to_base)

Description

Converts numbers between different number bases. Returns a string representation of the number N, converted from base from_base to base to_base.

Returns NULL if any argument is NULL, or if the second or third argument are not in the allowed range.

The argument N is interpreted as an integer, but may be specified as an integer or a string. The minimum base is 2 and the maximum base is 36. If to_base is a negative number, N is regarded as a signed number. Otherwise, N is treated as unsigned. CONV() works with 64-bit precision.

Some shortcuts for this function are also available: BIN(), OCT(), HEX(), UNHEX(). Also, MariaDB allows binary literal values and hexadecimal literal values.

Examples

SELECT CONV('a',16,2);
+----------------+
| CONV('a',16,2) |
+----------------+
| 1010           |
+----------------+

SELECT CONV('6E',18,8);
+-----------------+
| CONV('6E',18,8) |
+-----------------+
| 172             |
+-----------------+

SELECT CONV(-17,10,-18);
+------------------+
| CONV(-17,10,-18) |
+------------------+
| -H               |
+------------------+

SELECT CONV(12+'10'+'10'+0xa,10,10);
+------------------------------+
| CONV(12+'10'+'10'+0xa,10,10) |
+------------------------------+
| 42                           |
+------------------------------+

COS

Syntax

COS(X)

Description

Returns the cosine of X, where X is given in radians.

Examples

SELECT COS(PI());
+-----------+
| COS(PI()) |
+-----------+
|        -1 |
+-----------

COT

Syntax

COT(X)

Description

Returns the cotangent of X.

Examples

SELECT COT(42);
+--------------------+
| COT(42)            |
+--------------------+
| 0.4364167060752729 |
+--------------------+

SELECT COT(12);
+---------------------+
| COT(12)             |
+---------------------+
| -1.5726734063976893 |
+---------------------+

SELECT COT(0);
ERROR 1690 (22003): DOUBLE value is out of range in 'cot(0)'

CRC32

Syntax

<= MariaDB 10.7

CRC32(expr)

From MariaDB 10.8

CRC32([par,]expr)

Description

Computes a cyclic redundancy check (CRC) value and returns a 32-bit unsigned value. The result is NULL if the argument is NULL. The argument is expected to be a string and (if possible) is treated as one if it is not.

Uses the ISO 3309 polynomial that used by zlib and many others. MariaDB 10.8 introduced the CRC32C() function, which uses the alternate Castagnoli polynomia.

MariaDB starting with 10.8

Often, CRC is computed in pieces. To facilitate this, MariaDB 10.8.0 introduced an optional parameter: CRC32('MariaDB')=CRC32(CRC32('Maria'),'DB').

Examples

SELECT CRC32('MariaDB');
+------------------+
| CRC32('MariaDB') |
+------------------+
|       4227209140 |
+------------------+

SELECT CRC32('mariadb');
+------------------+
| CRC32('mariadb') |
+------------------+
|       2594253378 |
+------------------+

From MariaDB 10.8.0

SELECT CRC32(CRC32('Maria'),'DB');
+----------------------------+
| CRC32(CRC32('Maria'),'DB') |
+----------------------------+
|                 4227209140 |
+----------------------------+

See Also

DEGREES

Syntax

DEGREES(X)

Description

Returns the argument X, converted from radians to degrees.

This is the converse of the RADIANS() function.

Examples

SELECT DEGREES(PI());
+---------------+
| DEGREES(PI()) |
+---------------+
|           180 |
+---------------+

SELECT DEGREES(PI() / 2);
+-------------------+
| DEGREES(PI() / 2) |
+-------------------+
|                90 |
+-------------------+

SELECT DEGREES(45);
+-----------------+
| DEGREES(45)     |
+-----------------+
| 2578.3100780887 |
+-----------------+

EXP

Syntax

EXP(X)

Description

Returns the value of e (the base of natural logarithms) raised to the power of X. The inverse of this function is LOG() (using a single argument only) or LN().

If X is NULL, this function returns NULL.

Examples

SELECT EXP(2);
+------------------+
| EXP(2)           |
+------------------+
| 7.38905609893065 |
+------------------+

SELECT EXP(-2);
+--------------------+
| EXP(-2)            |
+--------------------+
| 0.1353352832366127 |
+--------------------+

SELECT EXP(0);
+--------+
| EXP(0) |
+--------+
|      1 |
+--------+

SELECT EXP(NULL);
+-----------+
| EXP(NULL) |
+-----------+
|      NULL |
+-----------+

FLOOR

Syntax

FLOOR(X)

Description

Returns the largest integer value not greater than X.

Examples

SELECT FLOOR(1.23);
+-------------+
| FLOOR(1.23) |
+-------------+
|           1 |
+-------------+

SELECT FLOOR(-1.23);
+--------------+
| FLOOR(-1.23) |
+--------------+
|           -2 |
+--------------+

LN

Syntax

LN(X)

Description

Returns the natural logarithm of X; that is, the base-e logarithm of X. If X is less than or equal to 0, or NULL, then NULL is returned.

The inverse of this function is EXP().

Examples

SELECT LN(2);
+-------------------+
| LN(2)             |
+-------------------+
| 0.693147180559945 |
+-------------------+

SELECT LN(-2);
+--------+
| LN(-2) |
+--------+
|   NULL |
+--------+

LOG

Syntax

LOG(X), LOG(B,X)

Description

If called with one parameter, this function returns the natural logarithm of X. If X is less than or equal to 0, then NULL is returned.

If called with two parameters, it returns the logarithm of X to the base B. If B is <= 1 or X <= 0, the function returns NULL.

If any argument is NULL, the function returns NULL.

The inverse of this function (when called with a single argument) is the EXP() function.

Examples

LOG(X):

SELECT LOG(2);
+-------------------+
| LOG(2)            |
+-------------------+
| 0.693147180559945 |
+-------------------+

SELECT LOG(-2);
+---------+
| LOG(-2) |
+---------+
|    NULL |
+---------+

LOG(B,X)

SELECT LOG(2,16);
+-----------+
| LOG(2,16) |
+-----------+
|         4 |
+-----------+

SELECT LOG(3,27);
+-----------+
| LOG(3,27) |
+-----------+
|         3 |
+-----------+

SELECT LOG(3,1);
+----------+
| LOG(3,1) |
+----------+
|        0 |
+----------+

SELECT LOG(3,0);
+----------+
| LOG(3,0) |
+----------+
|     NULL |
+----------+

LOG10

Syntax

LOG10(X)

Description

Returns the base-10 logarithm of X.

Examples

SELECT LOG10(2);
+-------------------+
| LOG10(2)          |
+-------------------+
| 0.301029995663981 |
+-------------------+

SELECT LOG10(100);
+------------+
| LOG10(100) |
+------------+
|          2 |
+------------+

SELECT LOG10(-100);
+-------------+
| LOG10(-100) |
+-------------+
|        NULL |
+-------------+

LOG2

Syntax

LOG2(X)

Description

Returns the base-2 logarithm of X.

Examples

SELECT LOG2(4398046511104);
+---------------------+
| LOG2(4398046511104) |
+---------------------+
|                  42 |
+---------------------+

SELECT LOG2(65536);
+-------------+
| LOG2(65536) |
+-------------+
|          16 |
+-------------+

SELECT LOG2(-100);
+------------+
| LOG2(-100) |
+------------+
|       NULL |
+------------+

MOD

Syntax

MOD(N,M), N % M, N MOD M

Description

Modulo operation. Returns the remainder of N divided by M. See also Modulo Operator.

If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, any number modulus zero produces an error. Otherwise, it returns NULL.

The integer part of a division can be obtained using DIV.

Examples

SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
|        42 |
+-----------+

SELECT MOD(234, 10);
+--------------+
| MOD(234, 10) |
+--------------+
|            4 |
+--------------+

SELECT 253 % 7;
+---------+
| 253 % 7 |
+---------+
|       1 |
+---------+

SELECT MOD(29,9);
+-----------+
| MOD(29,9) |
+-----------+
|         2 |
+-----------+

SELECT 29 MOD 9;
+----------+
| 29 MOD 9 |
+----------+
|        2 |
+----------+

OCT

Syntax

OCT(N)

Description

Returns a string representation of the octal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,8). Returns NULL if N is NULL.

Examples

SELECT OCT(34);
+---------+
| OCT(34) |
+---------+
| 42      |
+---------+

SELECT OCT(12);
+---------+
| OCT(12) |
+---------+
| 14      |
+---------+

See Also

PI

Syntax

PI()

Description

Returns the value of π (pi). The default number of decimal places displayed is six, but MariaDB uses the full double-precision value internally.

Examples

SELECT PI();
+----------+
| PI()     |
+----------+
| 3.141593 |
+----------+

SELECT PI()+0.0000000000000000000000;
+-------------------------------+
| PI()+0.0000000000000000000000 |
+-------------------------------+
|      3.1415926535897931159980 |
+-------------------------------+

POW

Syntax

POW(X,Y)

Description

Returns the value of X raised to the power of Y.

POWER() is a synonym.

Examples

SELECT POW(2,3);
+----------+
| POW(2,3) |
+----------+
|        8 |
+----------+

SELECT POW(2,-2);
+-----------+
| POW(2,-2) |
+-----------+
|      0.25 |
+-----------+

POWER

Syntax

POWER(X,Y)

Description

This is a synonym for POW(), which returns the value of X raised to the power of Y.

RADIANS

Syntax

RADIANS(X)

Description

Returns the argument X, converted from degrees to radians. Note that π radians equals 180 degrees.

This is the converse of the DEGREES() function.

Examples

SELECT RADIANS(45);
+-------------------+
| RADIANS(45)       |
+-------------------+
| 0.785398163397448 |
+-------------------+

SELECT RADIANS(90);
+-----------------+
| RADIANS(90)     |
+-----------------+
| 1.5707963267949 |
+-----------------+

SELECT RADIANS(PI());
+--------------------+
| RADIANS(PI())      |
+--------------------+
| 0.0548311355616075 |
+--------------------+

SELECT RADIANS(180);
+------------------+
| RADIANS(180)     |
+------------------+
| 3.14159265358979 |
+------------------+

RAND

Syntax

RAND(), RAND(N)

Description

Returns a random DOUBLE precision floating point value v in the range 0 <= v < 1.0. If a constant integer argument N is specified, it is used as the seed value, which produces a repeatable sequence of column values. In the example below, note that the sequences of values produced by RAND(3) is the same both places where it occurs.

In a WHERE clause, RAND() is evaluated each time the WHERE is executed.

Statements using the RAND() function are not safe for statement-based replication.

Practical uses

The expression to get a random integer from a given range is the following:

FLOOR(min_value + RAND() * (max_value - min_value +1))

RAND() is often used to read random rows from a table, as follows:

SELECT * FROM my_table ORDER BY RAND() LIMIT 10;

Note, however, that this technique should never be used on a large table as it will be extremely slow. MariaDB will read all rows in the table, generate a random value for each of them, order them, and finally will apply the LIMIT clause.

Examples

CREATE TABLE t (i INT);

INSERT INTO t VALUES(1),(2),(3);

SELECT i, RAND() FROM t;
+------+-------------------+
| i    | RAND()            |
+------+-------------------+
|    1 | 0.255651095188829 |
|    2 | 0.833920199269355 |
|    3 |  0.40264774151393 |
+------+-------------------+

SELECT i, RAND(3) FROM t;
+------+-------------------+
| i    | RAND(3)           |
+------+-------------------+
|    1 |  0.90576975597606 |
|    2 | 0.373079058130345 |
|    3 | 0.148086053457191 |
+------+-------------------+

SELECT i, RAND() FROM t;
+------+-------------------+
| i    | RAND()            |
+------+-------------------+
|    1 | 0.511478140495232 |
|    2 | 0.349447508668012 |
|    3 | 0.212803152588013 |
+------+-------------------+

Using the same seed, the same sequence will be returned:

SELECT i, RAND(3) FROM t;
+------+-------------------+
| i    | RAND(3)           |
+------+-------------------+
|    1 |  0.90576975597606 |
|    2 | 0.373079058130345 |
|    3 | 0.148086053457191 |
+------+-------------------+

Generating a random number from 5 to 15:

SELECT FLOOR(5 + (RAND() * 11));

See Also

ROUND

Syntax

ROUND(X), ROUND(X,D)

Description

Rounds the argument X to D decimal places. The rounding algorithm depends on the data type of X. D defaults to 0 if not specified. D can be negative to cause D digits left of the decimal point of the value X to become zero.

Examples

SELECT ROUND(-1.23);
+--------------+
| ROUND(-1.23) |
+--------------+
|           -1 |
+--------------+

SELECT ROUND(-1.58);
+--------------+
| ROUND(-1.58) |
+--------------+
|           -2 |
+--------------+

SELECT ROUND(1.58); 
+-------------+
| ROUND(1.58) |
+-------------+
|           2 |
+-------------+

SELECT ROUND(1.298, 1);
+-----------------+
| ROUND(1.298, 1) |
+-----------------+
|             1.3 |
+-----------------+

SELECT ROUND(1.298, 0);
+-----------------+
| ROUND(1.298, 0) |
+-----------------+
|               1 |
+-----------------+

SELECT ROUND(23.298, -1);
+-------------------+
| ROUND(23.298, -1) |
+-------------------+
|                20 |
+-------------------+

SIGN

Syntax

SIGN(X)

Description

Returns the sign of the argument as -1, 0, or 1, depending on whether X is negative, zero, or positive.

Examples

SELECT SIGN(-32);
+-----------+
| SIGN(-32) |
+-----------+
|        -1 |
+-----------+

SELECT SIGN(0);
+---------+
| SIGN(0) |
+---------+
|       0 |
+---------+

SELECT SIGN(234);
+-----------+
| SIGN(234) |
+-----------+
|         1 |
+-----------+

See Also

SIN

Syntax

SIN(X)

Description

Returns the sine of X, where X is given in radians.

Examples

SELECT SIN(1.5707963267948966);
+-------------------------+
| SIN(1.5707963267948966) |
+-------------------------+
|                       1 |
+-------------------------+

SELECT SIN(PI());
+----------------------+
| SIN(PI())            |
+----------------------+
| 1.22460635382238e-16 |
+----------------------+

SELECT ROUND(SIN(PI()));
+------------------+
| ROUND(SIN(PI())) |
+------------------+
|                0 |
+------------------+

SQRT

Syntax

SQRT(X)

Description

Returns the square root of X. If X is negative, NULL is returned.

Examples

SELECT SQRT(4);
+---------+
| SQRT(4) |
+---------+
|       2 |
+---------+

SELECT SQRT(20);
+------------------+
| SQRT(20)         |
+------------------+
| 4.47213595499958 |
+------------------+

SELECT SQRT(-16);
+-----------+
| SQRT(-16) |
+-----------+
|      NULL |
+-----------+

SELECT SQRT(1764);
+------------+
| SQRT(1764) |
+------------+
|         42 |
+------------+

TAN

Syntax

TAN(X)

Description

Returns the tangent of X, where X is given in radians.

Examples

SELECT TAN(0.7853981633974483);
+-------------------------+
| TAN(0.7853981633974483) |
+-------------------------+
|      0.9999999999999999 |
+-------------------------+

SELECT TAN(PI());
+-----------------------+
| TAN(PI())             |
+-----------------------+
| -1.22460635382238e-16 |
+-----------------------+

SELECT TAN(PI()+1);
+-----------------+
| TAN(PI()+1)     |
+-----------------+
| 1.5574077246549 |
+-----------------+

SELECT TAN(RADIANS(PI()));
+--------------------+
| TAN(RADIANS(PI())) |
+--------------------+
| 0.0548861508080033 |
+--------------------+

TRUNCATE

This page documents the TRUNCATE function. See TRUNCATE TABLE for the DDL statement.

Syntax

TRUNCATE(X,D)

Description

Returns the number X, truncated to D decimal places. If D is 0, the result has no decimal point or fractional part. D can be negative to cause D digits left of the decimal point of the value X to become zero.

Examples

SELECT TRUNCATE(1.223,1);
+-------------------+
| TRUNCATE(1.223,1) |
+-------------------+
|               1.2 |
+-------------------+

SELECT TRUNCATE(1.999,1);
+-------------------+
| TRUNCATE(1.999,1) |
+-------------------+
|               1.9 |
+-------------------+

SELECT TRUNCATE(1.999,0); 
+-------------------+
| TRUNCATE(1.999,0) |
+-------------------+
|                 1 |
+-------------------+

SELECT TRUNCATE(-1.999,1);
+--------------------+
| TRUNCATE(-1.999,1) |
+--------------------+
|               -1.9 |
+--------------------+

SELECT TRUNCATE(122,-2);
+------------------+
| TRUNCATE(122,-2) |
+------------------+
|              100 |
+------------------+

SELECT TRUNCATE(10.28*100,0);
+-----------------------+
| TRUNCATE(10.28*100,0) |
+-----------------------+
|                  1028 |
+-----------------------+

See Also

Plugin Overview

Plugins are server components that enhance MariaDB in some way. These can be anything from new storage engines, plugins for enhancing full-text parsing, or even small enhancements, such as a plugin to get a timestamp as an integer.

Querying Plugin Information

There are a number of ways to see which plugins are currently active.

A server almost always has a large number of active plugins, because the server contains a large number of built-in plugins, which are active by default and cannot be uninstalled.

Querying Plugin Information with SHOW PLUGINS

The SHOW PLUGINS statement can be used to query information about all active plugins.

For example:

SHOW PLUGINS\G;
********************** 1. row **********************
   Name: binlog
 Status: ACTIVE
   Type: STORAGE ENGINE
Library: NULL
License: GPL
********************** 2. row **********************
   Name: mysql_native_password
 Status: ACTIVE
   Type: AUTHENTICATION
Library: NULL
License: GPL
********************** 3. row **********************
   Name: mysql_old_password
 Status: ACTIVE
   Type: AUTHENTICATION
Library: NULL
License: GPL
...

If a plugin's Library column has a NULL value, then the plugin is built-in, and it cannot be uninstalled.

Querying Plugin Information with information_schema.PLUGINS

The information_schema.PLUGINS table can be queried to get more detailed information about plugins.

For example:

SELECT * FROM information_schema.PLUGINS\G
...
*************************** 6. row ***************************
           PLUGIN_NAME: CSV
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: STORAGE ENGINE
   PLUGIN_TYPE_VERSION: 100003.0
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: Brian Aker, MySQL AB
    PLUGIN_DESCRIPTION: CSV storage engine
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 7. row ***************************
           PLUGIN_NAME: MEMORY
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: STORAGE ENGINE
   PLUGIN_TYPE_VERSION: 100003.0
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: MySQL AB
    PLUGIN_DESCRIPTION: Hash based, stored in memory, useful for temporary tables
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
...

If a plugin's PLUGIN_LIBRARY column has the NULL value, then the plugin is built-in, and it cannot be uninstalled.

Querying Plugin Information with mysql.plugin

The mysql.plugin table can be queried to get information about installed plugins.

This table only contains information about plugins that have been installed via the following methods:

This table does not contain information about:

This table only contains enough information to reload the plugin when the server is restarted, which means it only contains the plugin name and the plugin library.

For example:

SELECT * FROM mysql.plugin;

+------+------------+
| name | dl         |
+------+------------+
| PBXT | libpbxt.so |
+------+------------+

Installing a Plugin

There are three primary ways to install a plugin:

  • A plugin can be installed dynamically with an SQL statement.
  • A plugin can be installed with a mysqld option, but it requires a server restart.
  • A plugin can be installed with the mysql_plugin utility, while the server is completely offline.

When you are installing a plugin, you also have to ensure that:

  • The server's plugin directory is properly configured, and the plugin's library is in the plugin directory.
  • The server's minimum plugin maturity is properly configured, and the plugin is mature enough to be installed.

Installing a Plugin Dynamically

A plugin can be installed dynamically by executing either the INSTALL SONAME or the INSTALL PLUGIN statement.

If a plugin is installed with one of these statements, then a record will be added to the mysql.plugins table for the plugin. This means that the plugin will automatically be loaded every time the server restarts, unless specifically uninstalled or deactivated.

Installing a Plugin with INSTALL SONAME

You can install a plugin dynamically by executing the INSTALL SONAME statement. INSTALL SONAME installs all plugins from the given plugin library. This could be required for some plugin libraries.

For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin), you could execute the following:

INSTALL SONAME 'server_audit';

Installing a Plugin with INSTALL PLUGIN

You can install a plugin dynamically by executing the INSTALL PLUGIN statement. INSTALL PLUGIN installs a single plugin from the given plugin library.

For example, to install the server_audit audit plugin from the server_audit plugin library, you could execute the following:

INSTALL PLUGIN server_audit SONAME 'server_audit';

Installing a Plugin with Plugin Load Options

A plugin can be installed with a mysqld option by providing either the --plugin-load-add or the --plugin-load option.

If a plugin is installed with one of these options, then a record will not be added to the mysql.plugins table for the plugin. This means that if the server is restarted without the same option set, then the plugin will not automatically be loaded.

Installing a Plugin with --plugin-load-add

You can install a plugin with the --plugin-load-add option by specifying the option as a command-line argument to mysqld or by specifying the option in a relevant server option group in an option file.

The --plugin-load-add option uses the following format:

  • Plugins can be specified in the format name=library, where name is the plugin name and library is the plugin library. This format installs a single plugin from the given plugin library.
  • Plugins can also be specified in the format library, where library is the plugin library. This format installs all plugins from the given plugin library.
  • Multiple plugins can be specified by separating them with semicolons.

For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin) and also the ed25519 authentication plugin from the auth_ed25519 plugin library, you could set the option to the following values on the command-line:

$ mysqld --user=mysql --plugin-load-add='server_audit' --plugin-load-add='ed25519=auth_ed25519'

You could also set the option to the same values in an option file:

[mariadb]
...
plugin_load_add = server_audit
plugin_load_add = ed25519=auth_ed25519

Special care must be taken when specifying both the --plugin-load option and the --plugin-load-add option together. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use. See Specifying Multiple Plugin Load Options for more information.

Installing a Plugin with --plugin-load

You can install a plugin with the --plugin-load option by specifying the option as a command-line argument to mysqld or by specifying the option in a relevant server option group in an option file.

The --plugin-load option uses the following format:

  • Plugins can be specified in the format name=library, where name is the plugin name and library is the plugin library. This format installs a single plugin from the given plugin library.
  • Plugins can also be specified in the format library, where library is the plugin library. This format installs all plugins from the given plugin library.
  • Multiple plugins can be specified by separating them with semicolons.

For example, to install all plugins in the server_audit plugin library (which is currently only the server_audit audit plugin) and also the ed25519 authentication plugin from the auth_ed25519 plugin library, you could set the option to the following values on the command-line:

$ mysqld --user=mysql --plugin-load='server_audit;ed25519=auth_ed25519'

You could also set the option to the same values in an option file:

[mariadb]
...
plugin_load = server_audit;ed25519=auth_ed25519

Special care must be taken when specifying the --plugin-load option multiple times, or when specifying both the --plugin-load option and the --plugin-load-add option together. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use. See Specifying Multiple Plugin Load Options for more information.

Specifying Multiple Plugin Load Options

Special care must be taken when specifying the --plugin-load option multiple times, or when specifying both the --plugin-load option and the --plugin-load-add option. The --plugin-load option resets the plugin load list, and this can cause unexpected problems if you are not aware. The --plugin-load-add option does not reset the plugin load list, so it is much safer to use.

This can have the following consequences:

  • If the --plugin-load option is specified multiple times, then only the last instance will have any effect. For example, in the following case, the first instance of the option is reset:
[mariadb]
...
plugin_load = server_audit
plugin_load = ed25519=auth_ed25519
[mariadb]
...
plugin_load_add = server_audit
plugin_load = ed25519=auth_ed25519
  • In contrast, if the --plugin-load option is specified before the --plugin-load-add option, then it will work fine, because the --plugin-load-add option does not reset the plugin load list. For example, in the following case, both plugins are properly loaded:
[mariadb]
...
plugin_load = server_audit
plugin_load_add = ed25519=auth_ed25519

Installing a Plugin with mysql_plugin

A plugin can be installed with the mysql_plugin utility if the server is completely offline.

The syntax is:

mysql_plugin [options] <plugin> ENABLE|DISABLE

For example, to install the server_audit audit plugin, you could execute the following:

mysql_plugin server_audit ENABLE

If a plugin is installed with this utility, then a record will be added to the mysql.plugins table for the plugin. This means that the plugin will automatically be loaded every time the server restarts, unless specifically uninstalled or deactivated.

Configuring the Plugin Directory

When a plugin is being installed, the server looks for the plugin's library in the server's plugin directory. This directory is configured by the plugin_dir system variable. This can be specified as a command-line argument to mysqld or it can be specified in a relevant server option group in an option file. For example:

[mariadb]
...
plugin_dir = /usr/lib64/mysql/plugin

Configuring the Minimum Plugin Maturity

When a plugin is being installed, the server compares the plugin's maturity level against the server's minimum allowed plugin maturity. This can help prevent users from using unstable plugins on production servers. This minimum plugin maturity is configured by the plugin_maturity system variable. This can be specified as a command-line argument to mysqld or it can be specified in a relevant server option group in an option file. For example:

[mariadb]
...
plugin_maturity = stable

Configuring Plugin Activation at Server Startup

A plugin will be loaded by default when the server starts if:

This behavior can be changed with special options that take the form --plugin-name. For example, for the server_audit audit plugin, the special option is called --server-audit.

The possible values for these special options are:

Option ValueDescription
OFFDisables the plugin without removing it from the mysql.plugins table.
ONEnables the plugin. If the plugin cannot be initialized, then the server will still continue starting up, but the plugin will be disabled.
FORCEEnables the plugin. If the plugin cannot be initialized, then the server will fail to start with an error.
FORCE_PLUS_PERMANENTEnables the plugin. If the plugin cannot be initialized, then the server will fail to start with an error. In addition, the plugin cannot be uninstalled with UNINSTALL SONAME or UNINSTALL PLUGIN while the server is running.

A plugin's status can be found by looking at the PLUGIN_STATUS column of the information_schema.PLUGINS table.

Uninstalling Plugins

Plugins that are found in the mysql.plugin table, that is those that were installed with INSTALL SONAME, INSTALL PLUGIN or mysql_plugin can be uninstalled in one of two ways:

Plugins that were enabled as a --plugin-load option do not need to be uninstalled. If --plugin-load is omitted the next time the server starts, or the plugin is not listed as one of the --plugin-load entries, the plugin will not be loaded.

UNINSTALL PLUGIN uninstalls a single installed plugin, while UNINSTALL SONAME uninstalls all plugins belonging to a given library.

See Also

MBR Definition

Description

The MBR (Minimum Bounding Rectangle), or Envelope is the bounding geometry, formed by the minimum and maximum (X,Y) coordinates:

Examples

((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))

MBRContains

Syntax

MBRContains(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangle of g1 contains the Minimum Bounding Rectangle of g2. This tests the opposite relationship as MBRWithin().

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');

SET @g2 = GeomFromText('Point(1 1)');

SELECT MBRContains(@g1,@g2), MBRContains(@g2,@g1);
+----------------------+----------------------+
| MBRContains(@g1,@g2) | MBRContains(@g2,@g1) |
+----------------------+----------------------+
|                    1 |                    0 |
+----------------------+----------------------+

MBREqual

Syntax

MBREqual(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 are the same.

Examples

SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 2)');
SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 2, 1 0, 0 0))');
SELECT MbrEqual(@g1,@g2);
+-------------------+
| MbrEqual(@g1,@g2) |
+-------------------+
|                 1 |
+-------------------+

SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 3)');
SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 4, 1 0, 0 0))');
SELECT MbrEqual(@g1,@g2);
+-------------------+
| MbrEqual(@g1,@g2) |
+-------------------+
|                 0 |
+-------------------+

MBRWithin

Syntax

MBRWithin(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangle of g1 is within the Minimum Bounding Rectangle of g2. This tests the opposite relationship as MBRContains().

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((0 0,0 5,5 5,5 0,0 0))');
SELECT MBRWithin(@g1,@g2), MBRWithin(@g2,@g1);
+--------------------+--------------------+
| MBRWithin(@g1,@g2) | MBRWithin(@g2,@g1) |
+--------------------+--------------------+
|                  1 |                  0 |
+--------------------+--------------------+

IF Function

Syntax

IF(expr1,expr2,expr3)

Description

If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL) then IF() returns expr2; otherwise it returns expr3. IF() returns a numeric or string value, depending on the context in which it is used.

Note: There is also an IF statement which differs from the IF() function described here.

Examples

SELECT IF(1>2,2,3);
+-------------+
| IF(1>2,2,3) |
+-------------+
|           3 |
+-------------+
SELECT IF(1<2,'yes','no');
+--------------------+
| IF(1<2,'yes','no') |
+--------------------+
| yes                |
+--------------------+
SELECT IF(STRCMP('test','test1'),'no','yes');
+---------------------------------------+
| IF(STRCMP('test','test1'),'no','yes') |
+---------------------------------------+
| no                                    |
+---------------------------------------+

See Also

There is also an IF statement, which differs from the IF() function described above.

MBRDisjoint

Syntax

MBRDisjoint(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 are disjoint. Two geometries are disjoint if they do not intersect, that is touch or overlap.

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECTmbrdisjoint(@g1,@g2);
+----------------------+
| mbrdisjoint(@g1,@g2) |
+----------------------+
|                    1 |
+----------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrdisjoint(@g1,@g2);
+----------------------+
| mbrdisjoint(@g1,@g2) |
+----------------------+
|                    0 |
+----------------------+

MBRIntersects

Syntax

MBRIntersects(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 intersect.

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrintersects(@g1,@g2);
+------------------------+
| mbrintersects(@g1,@g2) |
+------------------------+
|                      1 |
+------------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbrintersects(@g1,@g2);
+------------------------+
| mbrintersects(@g1,@g2) |
+------------------------+
|                      0 |
+------------------------+

MBROverlaps

Syntax

MBROverlaps(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 overlap. The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries.

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
|                    0 |
+----------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
|                    0 |
+----------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
|                    1 |
+----------------------+

MBRTouches

Syntax

MBRTouches(g1,g2)

Description

Returns 1 or 0 to indicate whether the Minimum Bounding Rectangles of the two geometries g1 and g2 touch. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other.

Examples

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
|                   0 |
+---------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
|                   1 |
+---------------------+

SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
|                   0 |
+---------------------+

CASE OPERATOR

Syntax

CASE value WHEN [compare_value] THEN result [WHEN [compare_value] THEN
result ...] [ELSE result] END

CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...]
[ELSE result] END

Description

The first version returns the result where value=compare_value. The second version returns the result for the first condition that is true. If there was no matching result value, the result after ELSE is returned, or NULL if there is no ELSE part.

There is also a CASE statement, which differs from the CASE operator described here.

Examples

SELECT CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END;
+------------------------------------------------------------+
| CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END |
+------------------------------------------------------------+
| one                                                        |
+------------------------------------------------------------+

SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;
+--------------------------------------------+
| CASE WHEN 1>0 THEN 'true' ELSE 'false' END |
+--------------------------------------------+
| true                                       |
+--------------------------------------------+


SELECT CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END;
+-----------------------------------------------------+
| CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END |
+-----------------------------------------------------+
|                                                NULL |
+-----------------------------------------------------+

IFNULL

Syntax

IFNULL(expr1,expr2)
NVL(expr1,expr2)

Description

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.

From MariaDB 10.3, NVL() is an alias for IFNULL().

Examples

SELECT IFNULL(1,0); 
+-------------+
| IFNULL(1,0) |
+-------------+
|           1 |
+-------------+

SELECT IFNULL(NULL,10);
+-----------------+
| IFNULL(NULL,10) |
+-----------------+
|              10 |
+-----------------+

SELECT IFNULL(1/0,10);
+----------------+
| IFNULL(1/0,10) |
+----------------+
|        10.0000 |
+----------------+

SELECT IFNULL(1/0,'yes');
+-------------------+
| IFNULL(1/0,'yes') |
+-------------------+
| yes               |
+-------------------+

See Also

NULLIF

Syntax

NULLIF(expr1,expr2)

Description

Returns NULL if expr1 = expr2 is true, otherwise returns expr1. This is the same as CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END.

Examples

SELECT NULLIF(1,1);
+-------------+
| NULLIF(1,1) |
+-------------+
|        NULL |
+-------------+

SELECT NULLIF(1,2);
+-------------+
| NULLIF(1,2) |
+-------------+
|           1 |
+-------------+

See Also

COMMIT

The COMMIT statement ends a transaction, saving any changes to the data so that they become visible to subsequent transactions. Also, unlocks metadata changed by current transaction. If autocommit is set to 1, an implicit commit is performed after each statement. Otherwise, all transactions which don't end with an explicit COMMIT are implicitly rollbacked and the changes are lost. The ROLLBACK statement can be used to do this explicitly.

The required syntax for the COMMIT statement is as follows:

COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]

COMMIT is the more important transaction terminator, as well as the more interesting one. The basic form of the COMMIT statement is simply the keyword COMMIT (the keyword WORK is simply noise and can be omitted without changing the effect).

The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated.

RELEASE tells the server to disconnect the client immediately after the current transaction.

There are NO RELEASE and AND NO CHAIN options. By default, commits do not RELEASE or CHAIN, but it's possible to change this default behavior with the completion_type server system variable. In this case, the AND NO CHAIN and NO RELEASE options override the server default.

See Also

DEALLOCATE / DROP PREPARE

Syntax

{DEALLOCATE | DROP} PREPARE stmt_name

Description

To deallocate a prepared statement produced with PREPARE, use a DEALLOCATE PREPARE statement that refers to the prepared statement name.

A prepared statement is implicitly deallocated when a new PREPARE command is issued. In that case, there is no need to use DEALLOCATE.

Attempting to execute a prepared statement after deallocating it results in an error, as if it was not prepared at all:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE

If the specified statement has not been PREPAREd, an error similar to the following will be produced:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to DEALLOCATE PREPARE

Example

See example in PREPARE.

See Also

EXECUTE Statement

Syntax

EXECUTE stmt_name
    [USING expression[, expression] ...]
MariaDB starting with 10.2.3

EXECUTE with expression as parameters was introduced in MariaDB 10.2.3. Before that one could only use variables (@var_name) as parameters.

Description

After preparing a statement with PREPARE, you execute it with an EXECUTE statement that refers to the prepared statement name. If the prepared statement contains any parameter markers, you must supply a USING clause that lists user variables containing the values to be bound to the parameters. Parameter values can be supplied only by user variables, and the USING clause must name exactly as many variables as the number of parameter markers in the statement.

You can execute a given prepared statement multiple times, passing different variables to it or setting the variables to different values before each execution.

If the specified statement has not been PREPAREd, an error similar to the following is produced:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE

Example

See example in PREPARE.

See Also

SAVEPOINT

Syntax

SAVEPOINT identifier
ROLLBACK [WORK] TO [SAVEPOINT] identifier
RELEASE SAVEPOINT identifier

Description

InnoDB supports the SQL statements SAVEPOINT, ROLLBACK TO SAVEPOINT, RELEASE SAVEPOINT and the optional WORK keyword for ROLLBACK.

Each savepoint must have a legal MariaDB identifier. A savepoint is a named sub-transaction.

Normally ROLLBACK undoes the changes performed by the whole transaction. When used with the TO clause, it undoes the changes performed after the specified savepoint, and erases all subsequent savepoints. However, all locks that have been acquired after the save point will survive. RELEASE SAVEPOINT does not rollback or commit any changes, but removes the specified savepoint.

When the execution of a trigger or a stored function begins, it is not possible to use statements which reference a savepoint which was defined from out of that stored program.

When a COMMIT (including implicit commits) or a ROLLBACK statement (with no TO clause) is performed, they act on the whole transaction, and all savepoints are removed.

Errors

If COMMIT or ROLLBACK is issued and no transaction was started, no error is reported.

If SAVEPOINT is issued and no transaction was started, no error is reported but no savepoint is created. When ROLLBACK TO SAVEPOINT or RELEASE SAVEPOINT is called for a savepoint that does not exist, an error like this is issued:

ERROR 1305 (42000): SAVEPOINT svp_name does not exist

UNLOCK TABLES

Syntax

UNLOCK TABLES

Contents

  1. Syntax
  2. Description

Description

UNLOCK TABLES explicitly releases any table locks held by the current session. See LOCK TABLES for more information.

In addition to releasing table locks acquired by the LOCK TABLES statement, the UNLOCK TABLES statement also releases the global read lock acquired by the FLUSH TABLES WITH READ LOCK statement. The FLUSH TABLES WITH READ LOCK statement is very useful for performing backups. See FLUSH for more information about FLUSH TABLES WITH READ LOCK.

XA Transactions

Overview

The MariaDB XA implementation is based on the X/Open CAE document Distributed Transaction Processing: The XA Specification. This document is published by The Open Group and available at http://www.opengroup.org/public/pubs/catalog/c193.htm.

XA transactions are designed to allow distributed transactions, where a transaction manager (the application) controls a transaction which involves multiple resources. Such resources are usually DBMSs, but could be resources of any type. The whole set of required transactional operations is called a global transaction. Each subset of operations which involve a single resource is called a local transaction. XA used a 2-phases commit (2PC). With the first commit, the transaction manager tells each resource to prepare an effective commit, and waits for a confirm message. The changes are not still made effective at this point. If any of the resources encountered an error, the transaction manager will rollback the global transaction. If all resources communicate that the first commit is successful, the transaction manager can require a second commit, which makes the changes effective.

In MariaDB, XA transactions can only be used with storage engines that support them. At least InnoDB, TokuDB, SPIDER and MyRocks support them. For InnoDB, until MariaDB 10.2, XA transactions can be disabled by setting the innodb_support_xa server system variable to 0. From MariaDB 10.3, XA transactions are always supported.

Like regular transactions, XA transactions create metadata locks on accessed tables.

XA transactions require REPEATABLE READ as a minimum isolation level. However, distributed transactions should always use SERIALIZABLE.

Trying to start more than one XA transaction at the same time produces a 1400 error (SQLSTATE 'XAE09'). The same error is produced when attempting to start an XA transaction while a regular transaction is in effect. Trying to start a regular transaction while an XA transaction is in effect produces a 1399 error (SQLSTATE 'XAE07').

The statements that cause an implicit COMMIT for regular transactions produce a 1400 error (SQLSTATE 'XAE09') if a XA transaction is in effect.

Internal XA vs External XA

XA transactions are an overloaded term in MariaDB. If a storage engine is XA-capable, it can mean one or both of these:

  • It supports MariaDB's internal two-phase commit API. This is transparent to the user. Sometimes this is called "internal XA", since MariaDB's internal transaction coordinator log can handle coordinating these transactions.
  • It supports XA transactions, with the XA START, XA PREPARE, XA COMMIT, etc. statements. Sometimes this is called "external XA", since it requires the use of an external transaction coordinator to use this feature properly.

Transaction Coordinator Log

If you have two or more XA-capable storage engines enabled, then a transaction coordinator log must be available.

There are currently two implementations of the transaction coordinator log:

  • Binary log-based transaction coordinator log
  • Memory-mapped file-based transaction coordinator log

If the binary log is enabled on a server, then the server will use the binary log-based transaction coordinator log. Otherwise, it will use the memory-mapped file-based transaction coordinator log.

See Transaction Coordinator Log for more information.

Syntax

XA {START|BEGIN} xid [JOIN|RESUME]

XA END xid [SUSPEND [FOR MIGRATE]]

XA PREPARE xid

XA COMMIT xid [ONE PHASE]

XA ROLLBACK xid

XA RECOVER [FORMAT=['RAW'|'SQL']]

xid: gtrid [, bqual [, formatID ]]

The interface to XA transactions is a set of SQL statements starting with XA. Each statement changes a transaction's state, determining which actions it can perform. A transaction which does not exist is in the NON-EXISTING state.

XA START (or BEGIN) starts a transaction and defines its xid (a transaction identifier). The JOIN or RESUME keywords have no effect. The new transaction will be in ACTIVE state.

The xid can have 3 components, though only the first one is mandatory. gtrid is a quoted string representing a global transaction identifier. bqual is a quoted string representing a local transaction identifier. formatID is an unsigned integer indicating the format used for the first two components; if not specified, defaults to 1. MariaDB does not interpret in any way these components, and only uses them to identify a transaction. xids of transactions in effect must be unique.

XA END declares that the specified ACTIVE transaction is finished and it changes its state to IDLE. SUSPEND [FOR MIGRATE] has no effect.

XA PREPARE prepares an IDLE transaction for commit, changing its state to PREPARED. This is the first commit.

XA COMMIT definitely commits and terminates a transaction which has already been PREPARED. If the ONE PHASE clause is specified, this statements performs a 1-phase commit on an IDLE transaction.

XA ROLLBACK rolls back and terminates an IDLE or PREPARED transaction.

XA RECOVER shows information about all PREPARED transactions.

When trying to execute an operation which is not allowed for the transaction's current state, an error is produced:

XA COMMIT 'test' ONE PHASE;
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the  ACTIVE state

XA COMMIT 'test2';
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the  NON-EXISTING state

XA RECOVER

The XA RECOVER statement shows information about all transactions which are in the PREPARED state. It does not matter which connection created the transaction: if it has been PREPARED, it appears. But this does not mean that a connection can commit or rollback a transaction which was started by another connection. Note that transactions using a 1-phase commit are never in the PREPARED state, so they cannot be shown by XA RECOVER.

XA RECOVER produces four columns:

XA RECOVER;
+----------+--------------+--------------+------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+------+
|        1 |            4 |            0 | test |
+----------+--------------+--------------+------+
MariaDB starting with 10.3.3

You can use XA RECOVER FORMAT='SQL' to get the data in a human readable form that can be directly copy-pasted into XA COMMIT or XA ROLLBACK. This is particularly useful for binary xid generated by some transaction coordinators.

formatID is the formatID part of xid.

data are the gtrid and bqual parts of xid, concatenated.

gtrid_length and bqual_length are the lengths of gtrid and bqual, respectevely.

Examples

2-phases commit:

XA START 'test';

INSERT INTO t VALUES (1,2);

XA END 'test';

XA PREPARE 'test';

XA COMMIT 'test';

1-phase commit:

XA START 'test';

INSERT INTO t VALUES (1,2);

XA END 'test';

XA COMMIT 'test' ONE PHASE;

Human-readable:

xa start '12\r34\t67\v78', 'abc\ndef', 3;

insert t1 values (40);

xa end '12\r34\t67\v78', 'abc\ndef', 3;

xa prepare '12\r34\t67\v78', 'abc\ndef', 3;

xa recover format='RAW';
+----------+--------------+--------------+--------------------+
| formatID | gtrid_length | bqual_length | data               |
+----------+--------------+--------------+--------------------+
34      67v78abc       11 |            7 | 12
def |
+----------+--------------+--------------+--------------------+

xa recover format='SQL';
+----------+--------------+--------------+-----------------------------------------------+
| formatID | gtrid_length | bqual_length | data                                          |
+----------+--------------+--------------+-----------------------------------------------+
|        3 |           11 |            7 | X'31320d3334093637763738',X'6162630a646566',3 |
+----------+--------------+--------------+-----------------------------------------------+

xa rollback X'31320d3334093637763738',X'6162630a646566',3;

Known Issues

MariaDB Galera Cluster

MariaDB Galera Cluster does not support XA transactions.

However, MariaDB Galera Cluster builds include a built-in plugin called wsrep. Prior to MariaDB 10.4.3, this plugin was internally considered an XA-capable storage engine. Consequently, these MariaDB Galera Cluster builds have multiple XA-capable storage engines by default, even if the only "real" storage engine that supports external XA transactions enabled on these builds by default is InnoDB. Therefore, when using one these builds MariaDB would be forced to use a transaction coordinator log by default, which could have performance implications.

See Transaction Coordinator Log Overview: MariaDB Galera Cluster for more information.

Authentication from MariaDB 10.4

MariaDB starting with 10.4

MariaDB 10.4 introduces a number of changes to the authentication process, intended to make things easier and more intuitive.

Overview

There are four new main features in 10.4 relating to authentication:

  • It is possible to use more than one authentication plugin for each user account. For example, this can be useful to slowly migrate users to the more secure ed25519 authentication plugin over time, while allowing the old mysql_native_password authentication plugin as an alternative for the transitional period.
  • The root@localhost user account created by mysql_install_db is created with the ability to use two authentication plugins.
    • First, it is configured to try to use the unix_socket authentication plugin. This allows the root@localhost user to login without a password via the local Unix socket file defined by the socket system variable, as long as the login is attempted from a process owned by the operating system root user account.
    • Second, if authentication fails with the unix_socket authentication plugin, then it is configured to try to use the mysql_native_password authentication plugin. However, an invalid password is initially set, so in order to authenticate this way, a password must be set with SET PASSWORD.
    • However, just using the unix_socket authentication plugin may be fine for many users, and it is very secure. You may want to try going without password authentication to see how well it works for you. Remember, the best way to keep your password safe is not to have one!
  • All user accounts, passwords, and global privileges are now stored in the mysql.global_priv table. The mysql.user table still exists and has exactly the same set of columns as before, but it’s now a view that references the mysql.global_priv table. Tools that analyze the mysql.user table should continue to work as before. From MariaDB 10.4.13, the dedicated mariadb.sys user is created as the definer of this view. Previously root was the definer, which resulted in privilege problems when this username was changed.
  • MariaDB 10.4 adds supports for User Password Expiry, which is not active by default.

Description

As a result of the above changes, the open-for-everyone all-powerful root account is finally gone. And installation scripts will no longer demand that you “PLEASE REMEMBER TO SET A PASSWORD FOR THE MariaDB root USER !”, because the root account is securely created automatically.

Two all-powerful accounts are created by default — root and the OS user that owns the data directory, typically mysql. They are created as:

CREATE USER root@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid'
CREATE USER mysql@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid'

Using unix_socket means that if you are the system root user, you can login as root@locahost without a password. This technique was pioneered by Otto Kekäläinen in Debian MariaDB packages and has been successfully used in Debian since as early as MariaDB 10.0.

It is based on a simple fact that asking the system root for a password adds no extra security — root has full access to all the data files and all process memory anyway. But not asking for a password means, there is no root password to forget (no need for the numerous tutorials on “how to reset MariaDB root password”). And if you want to script some tedious database work, there is no need to store the root password in plain text for the script to use (no need for debian-sys-maint user).

Still, some users may wish to log in as MariaDB root without using sudo. Hence the old authentication method — conventional MariaDB password — is still available. By default it is disabled (“invalid” is not a valid password hash), but one can set the password with a usual SET PASSWORD statement. And still retain the password-less access via sudo.

If you install MariaDB locally (say from a tarball), you would not want to use sudo to be able to login. This is why MariaDB creates a second all-powerful user with the same name as a system user that owns the data directory. In local (not system-wide) installations, this will be the user who installed MariaDB — they automatically get convenient password-less root-like access, because they can access all the data files anyway.

Even if MariaDB is installed system-wide, you may not want to run your database maintenance scripts as system root — now you can run them as system mysql user. And you will know that they will never destroy your entire system, even if you make a typo in a shell script.

However, seasoned MariaDB DBAs who are used to the old ways do need to makes some changes. See the examples below for common tasks.

Cookbook

After installing MariaDB system-wide the first thing you’ve got used to doing is logging in into the unprotected root account and protecting it, that is, setting the root password:

$ sudo dnf install MariaDB-server
$ mysql -uroot
...
MariaDB> set password = password("XH4VmT3_jt");

This is not only unnecessary now, it will simply not work — there is no unprotected root account. To login as root use

$ sudo dnf install MariaDB-server
$ sudo mysql

Note that it implies you are connecting via the unix socket, not tcp. If you happen to have protocol=tcp in a system-wide /etc/my.cnf file, use sudo mysql --protocol=socket.

After installing MariaDB locally you’ve also used to connect to the unprotected root account using mysql -uroot. This will not work either, simply use mysql without specifying a username.

If you've forgotten your root password, no problem — you can still connect using sudo and change the password. And if you've also removed unix_socket authentication, to restore access do as follows:

  • restart MariaDB with --skip-grant-tables
  • login into the unprotected server
  • run FLUSH PRIVILEGES (note, before 10.4 this would’ve been the last step, not anymore). This disables --skip-grant-tables and allows you to change the stored authentication method
  • run SET PASSWORD FOR root@localhost to change the root password.

To view inside privilege tables, the old mysql.user table still exists. You can select from it as before, although you cannot update it anymore. It doesn’t show alternative authentication plugins and this was one of the reasons for switching to the mysql.global_priv table — complex authentication rules did not fit into rigid structure of a relational table. You can select from the new table, for example:

select concat(user, '@', host, ' => ', json_detailed(priv)) from mysql.global_priv;

Reverting to the Previous Authentication Method for root@localhost

If you don't want the root@localhost user account created by mysql_install_db to use unix_socket authentication by default, then there are a few ways to revert to the previous mysql_native_password authentication method for this user account.

Configuring mysql_install_db to Revert to the Previous Authentication Method

One way to revert to the previous mysql_native_password authentication method for the root@localhost user account is to execute mysql_install_db with a special option. If mysql_install_db is executed while --auth-root-authentication-method=normal is specified, then it will create the default user accounts using the default behavior of MariaDB 10.3 and before.

This means that the root@localhost user account will use mysql_native_password authentication by default. There are some other differences as well. See mysql_install_db: User Accounts Created by Default for more information.

For example, the option can be set on the command-line while running mysql_install_db:

mysql_install_db --user=mysql --datadir=/var/lib/mysql --auth-root-authentication-method=normal

The option can also be set in an option file in an option group supported by mysql_install_db. For example:

[mysql_install_db]
auth_root_authentication_method=normal

If the option is set in an option file and if mysql_install_db is executed, then mysql_install_db will read this option from the option file, and it will automatically set this option.

Altering the User Account to Revert to the Previous Authentication Method

If you have already installed MariaDB, and if the root@localhost user account is already using unix_socket authentication, then you can revert to the old mysql_native_password authentication method for the user account by executing the following:

ALTER USER root@localhost IDENTIFIED VIA mysql_native_password USING PASSWORD("verysecret")

See Also

ST_X

Syntax

ST_X(p)
X(p)

Description

Returns the X-coordinate value for the point p as a double-precision number.

ST_X() and X() are synonyms.

Examples

SET @pt = 'Point(56.7 53.34)';

SELECT X(GeomFromText(@pt));
+----------------------+
| X(GeomFromText(@pt)) |
+----------------------+
|                 56.7 |
+----------------------+

ST_Y

Syntax

ST_Y(p)
Y(p)

Description

Returns the Y-coordinate value for the point p as a double-precision number.

ST_Y() and Y() are synonyms.

Examples

SET @pt = 'Point(56.7 53.34)';

SELECT Y(GeomFromText(@pt));
+----------------------+
| Y(GeomFromText(@pt)) |
+----------------------+
|                53.34 |
+----------------------+

EXECUTE IMMEDIATE

MariaDB starting with 10.2.3

EXECUTE IMMEDIATE was introduced in MariaDB 10.2.3.

Syntax

EXECUTE IMMEDIATE statement

Description

EXECUTE IMMEDIATE executes a dynamic SQL statement created on the fly, which can reduce performance overhead.

For example:

EXECUTE IMMEDIATE 'SELECT 1' 

which is shorthand for:

prepare stmt from "select 1";
execute stmt;
deallocate prepare stmt;

EXECUTE IMMEDIATE supports complex expressions as prepare source and parameters:

EXECUTE IMMEDIATE CONCAT('SELECT COUNT(*) FROM ', 't1', ' WHERE a=?') USING 5+5;

Limitations: subselects and stored function calls are not supported as a prepare source.

The following examples return an error:

CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1';
EXECUTE IMMEDIATE f1();
ERROR 1970 (42000): EXECUTE IMMEDIATE does not support subqueries or stored functions

EXECUTE IMMEDIATE (SELECT 'SELECT * FROM t1');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that 
  corresponds to your MariaDB server version for the right syntax to use near 
  'SELECT 'SELECT * FROM t1')' at line 1

CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING f1();
ERROR 1970 (42000): EXECUTE..USING does not support subqueries or stored functions

EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING (SELECT 10);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that 
  corresponds to your MariaDB server version for the right syntax to use near 
  'SELECT 10)' at line 1

One can use a user or an SP variable as a workaround:

CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1';
SET @stmt=f1();
EXECUTE IMMEDIATE @stmt;

SET @stmt=(SELECT 'SELECT 1');
EXECUTE IMMEDIATE @stmt;

CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
SET @param=f1();
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param;

SET @param=(SELECT 10);
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param;

EXECUTE IMMEDIATE supports user variables and SP variables as OUT parameters

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1(OUT a INT)
BEGIN
  SET a:= 10;
END;
$$
DELIMITER ;
SET @a=2;
EXECUTE IMMEDIATE 'CALL p1(?)' USING @a;
SELECT @a;
+------+
| @a   |
+------+
|   10 |
+------+

Similar to PREPARE, EXECUTE IMMEDIATE is allowed in stored procedures but is not allowed in stored functions.

This example uses EXECUTE IMMEDIATE inside a stored procedure:

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
BEGIN
  EXECUTE IMMEDIATE 'SELECT 1';
END;
$$
DELIMITER ;
CALL p1;
+---+
| 1 |
+---+
| 1 |
+---+

This script returns an error:

DELIMITER $$
CREATE FUNCTION f1() RETURNS INT
BEGIN
  EXECUTE IMMEDIATE 'DO 1';
  RETURN 1;
END;
$$
ERROR 1336 (0A000): Dynamic SQL is not allowed in stored function or trigger

EXECUTE IMMEDIATE can use DEFAULT and IGNORE indicators as bind parameters:

CREATE OR REPLACE TABLE t1 (a INT DEFAULT 10);
EXECUTE IMMEDIATE 'INSERT INTO t1 VALUES (?)' USING DEFAULT;
SELECT * FROM t1;
+------+
| a    |
+------+
|   10 |
+------+

EXECUTE IMMEDIATE increments the Com_execute_immediate status variable, as well as the Com_stmt_prepare, Com_stmt_execute and Com_stmt_close status variables.

Note, EXECUTE IMMEDIATE does not increment the Com_execute_sql status variable. Com_execute_sql is used only for PREPARE..EXECUTE.

This session screenshot demonstrates how EXECUTE IMMEDIATE affects status variables:

SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE 
  ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');

+-----------------------+----------------+
| VARIABLE_NAME         | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 0              |
| COM_EXECUTE_SQL       | 0              |
| COM_STMT_CLOSE        | 0              |
| COM_STMT_EXECUTE      | 0              |
| COM_STMT_PREPARE      | 0              |
+-----------------------+----------------+

EXECUTE IMMEDIATE 'SELECT 1';
+---+
| 1 |
+---+
| 1 |
+---+

SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE 
  ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');
+-----------------------+----------------+
| VARIABLE_NAME         | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 1              |
| COM_EXECUTE_SQL       | 0              |
| COM_STMT_CLOSE        | 1              |
| COM_STMT_EXECUTE      | 1              |
| COM_STMT_PREPARE      | 1              |
+-----------------------+----------------+

Metadata Locking

MariaDB supports metadata locking. This means that when a transaction (including XA transactions) uses a table, it locks its metadata until the end of transaction. Non-transactional tables are also locked, as well as views and objects which are related to locked tables/views (stored functions, triggers, etc). When a connection tries to use a DDL statement (like an ALTER TABLE) which modifies a table that is locked, that connection is queued, and has to wait until it's unlocked. Using savepoints and performing a partial rollback does not release metadata locks.

LOCK TABLES ... WRITE are also queued. Some wrong statements which produce an error may not need to wait for the lock to be freed.

The metadata lock's timeout is determined by the value of the lock_wait_timeout server system variable (in seconds). However, note that its default value is 31536000 (1 year, MariaDB <= 10.2.3), or 86400 (1 day, MariaDB >= 10.2.4). If this timeout is exceeded, the following error is returned:

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table stores information about existing metadata locks.

MariaDB starting with 10.5.2

From MariaDB 10.5, the Performance Schema metadata_locks table contains metadata lock information.

Example

Let's use the following MEMORY (non-transactional) table:

CREATE TABLE t (a INT) ENGINE = MEMORY;

Connection 1 starts a transaction, and INSERTs a row into t:

START TRANSACTION;

INSERT INTO t SET a=1;

t's metadata is now locked by connection 1. Connection 2 tries to alter t, but has to wait:

ALTER TABLE t ADD COLUMN b INT;

Connection 2's prompt is blocked now.

Now connection 1 ends the transaction:

COMMIT;

...and connection 2 finally gets the output of its command:

Query OK, 1 row affected (35.23 sec)
Records: 1  Duplicates: 0  Warnings: 0

X

A synonym for ST_X.

Y

A synonym for ST_Y.

AES_DECRYPT

Syntax

AES_DECRYPT(crypt_str,key_str)

Description

This function allows decryption of data using the official AES (Advanced Encryption Standard) algorithm. For more information, see the description of AES_ENCRYPT().

DECODE

Syntax

DECODE(crypt_str,pass_str)

In Oracle mode from MariaDB 10.3.2:

DECODE(expr, search_expr, result_expr [, search_expr2, result_expr2 ...] [default_expr])

In all modes from MariaDB 10.3.2:

DECODE_ORACLE(expr, search_expr, result_expr [, search_expr2, result_expr2 ...] [default_expr])

Description

In the default mode, DECODE decrypts the encrypted string crypt_str using pass_str as the password. crypt_str should be a string returned from ENCODE(). The resulting string will be the original string only if pass_str is the same.

In Oracle mode from MariaDB 10.3.2, DECODE compares expr to the search expressions, in order. If it finds a match, the corresponding result expression is returned. If no matches are found, the default expression is returned, or NULL if no default is provided.

NULLs are treated as equivalent.

DECODE_ORACLE is a synonym for the Oracle-mode version of the function, and is available in all modes.

Examples

From MariaDB 10.3.2:

SELECT DECODE_ORACLE(2+1,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+1,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| found1                                                 |
+--------------------------------------------------------+

SELECT DECODE_ORACLE(2+4,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+4,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| found2                                                 |
+--------------------------------------------------------+

SELECT DECODE_ORACLE(2+2,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+2,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| default                                                |
+--------------------------------------------------------+

Nulls are treated as equivalent:

SELECT DECODE_ORACLE(NULL,NULL,'Nulls are equivalent','Nulls are not equivalent');
+----------------------------------------------------------------------------+
| DECODE_ORACLE(NULL,NULL,'Nulls are equivalent','Nulls are not equivalent') |
+----------------------------------------------------------------------------+
| Nulls are equivalent                                                       |
+----------------------------------------------------------------------------+

LOCK TABLES

Syntax

LOCK TABLE[S]
    tbl_name [[AS] alias] lock_type
    [, tbl_name [[AS] alias] lock_type] ...
    [WAIT n|NOWAIT]

lock_type:
    READ [LOCAL]
  | [LOW_PRIORITY] WRITE
  | WRITE CONCURRENT

UNLOCK TABLES

Description

The lock_type can be one of:

OptionDescription
READRead lock, no writes allowed
READ LOCALRead lock, but allow concurrent inserts
WRITEExclusive write lock. No other connections can read or write to this table
LOW_PRIORITY WRITEExclusive write lock, but allow new read locks on the table until we get the write lock.
WRITE CONCURRENTExclusive write lock, but allow READ LOCAL locks to the table.

MariaDB enables client sessions to acquire table locks explicitly for the purpose of cooperating with other sessions for access to tables, or to prevent other sessions from modifying tables during periods when a session requires exclusive access to them. A session can acquire or release locks only for itself. One session cannot acquire locks for another session or release locks held by another session.

Locks may be used to emulate transactions or to get more speed when updating tables.

LOCK TABLES explicitly acquires table locks for the current client session. Table locks can be acquired for base tables or views. To use LOCK TABLES, you must have the LOCK TABLES privilege, and the SELECT privilege for each object to be locked. See GRANT

For view locking, LOCK TABLES adds all base tables used in the view to the set of tables to be locked and locks them automatically. If you lock a table explicitly with LOCK TABLES, any tables used in triggers are also locked implicitly, as described in Triggers and Implicit Locks.

UNLOCK TABLES explicitly releases any table locks held by the current session.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Limitations

  • LOCK TABLES doesn't work when using Galera cluster. You may experience crashes or locks when used with Galera.
  • LOCK TABLES works on XtraDB/InnoDB tables only if the innodb_table_locks system variable is set to 1 (the default) and autocommit is set to 0 (1 is default). Please note that no error message will be returned on LOCK TABLES with innodb_table_locks = 0.
  • LOCK TABLES implicitly commits the active transaction, if any. Also, starting a transaction always releases all table locks acquired with LOCK TABLES. This means that there is no way to have table locks and an active transaction at the same time. The only exceptions are the transactions in autocommit mode. To preserve the data integrity between transactional and non-transactional tables, the GET_LOCK() function can be used.
  • When using LOCK TABLES on a TEMPORARY table, it will always be locked with a WRITE lock.
  • While a connection holds an explicit read lock on a table, it cannot modify it. If you try, the following error will be produced:
ERROR 1099 (HY000): Table 'tab_name' was locked with a READ lock and can't be updated
  • While a connection holds an explicit lock on a table, it cannot access a non-locked table. If you try, the following error will be produced:
ERROR 1100 (HY000): Table 'tab_name' was not locked with LOCK TABLES
  • While a connection holds an explicit lock on a table, it cannot issue the following: INSERT DELAYED, CREATE TABLE, CREATE TABLE ... LIKE, and DDL statements involving stored programs and views (except for triggers). If you try, the following error will be produced:
ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction
  • LOCK TABLES can not be used in stored routines - if you try, the following error will be produced on creation:
ERROR 1314 (0A000): LOCK is not allowed in stored procedures

See Also

PURGE BINARY LOGS

Syntax

PURGE { BINARY | MASTER } LOGS
    { TO 'log_name' | BEFORE datetime_expr }

Description

The PURGE BINARY LOGS statement deletes all the binary log files listed in the log index file prior to the specified log file name or date. BINARY and MASTER are synonyms. Deleted log files also are removed from the list recorded in the index file, so that the given log file becomes the first in the list.

The datetime expression is in the format 'YYYY-MM-DD hh:mm:ss'.

If a replica is active but has yet to read from a binary log file you attempt to delete, the statement will fail with an error. However, if the replica is not connected and has yet to read from a log file you delete, the file will be deleted, but the replica will be unable to continue replicating once it connects again.

This statement has no effect if the server was not started with the --log-bin option to enable binary logging.

To list the binary log files on the server, use SHOW BINARY LOGS. To see which files they are reading, use SHOW SLAVE STATUS (or SHOW REPLICA STATUS from MariaDB 10.5.1). You can only delete the files that are older than the oldest file that is used by the slaves.

To delete all binary log files, use RESET MASTER. To move to a new log file (for example if you want to remove the current log file), use FLUSH LOGS before you execute PURGE LOGS.

If the expire_logs_days server system variable is not set to 0, the server automatically deletes binary log files after the given number of days. From MariaDB 10.6, the binlog_expire_logs_seconds variable allows more precise control over binlog deletion, and takes precedence if both are non-zero.

Requires the SUPER privilege or, from MariaDB 10.5.2, the BINLOG ADMIN privilege, to run.

Examples

PURGE BINARY LOGS TO 'mariadb-bin.000063';
PURGE BINARY LOGS BEFORE '2013-04-21';
PURGE BINARY LOGS BEFORE '2013-04-22 09:55:22';

See Also

MD5

Syntax

MD5(str)

Description

Calculates an MD5 128-bit checksum for the string.

The return value is a 32-hex digit string, and as of MariaDB 5.5, is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

NULL is returned if the argument was NULL.

Examples

SELECT MD5('testing');
+----------------------------------+
| MD5('testing')                   |
+----------------------------------+
| ae2b1fca515949e5d54fb22b8ed95575 |
+----------------------------------+

PASSWORD

Syntax

PASSWORD(str)

Description

The PASSWORD() function is used for hashing passwords for use in authentication by the MariaDB server. It is not intended for use in other applications.

Calculates and returns a hashed password string from the plaintext password str. Returns an empty string (>= MariaDB 10.0.4) if the argument was NULL.

The return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables.

This is the function that is used for hashing MariaDB passwords for storage in the Password column of the user table (see privileges), usually used with the SET PASSWORD statement. It is not intended for use in other applications.

Until MariaDB 10.3, the return value is 41-bytes in length, and the first character is always '*'. From MariaDB 10.4, the function takes into account the authentication plugin where applicable (A CREATE USER or SET PASSWORD statement). For example, when used in conjunction with a user authenticated by the ed25519 plugin, the statement will create a longer hash:

CREATE USER edtest@localhost IDENTIFIED VIA ed25519 USING PASSWORD('secret');

CREATE USER edtest2@localhost IDENTIFIED BY 'secret';

SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv
  WHERE user LIKE 'edtest%'\G
*************************** 1. row ***************************
CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)): edtest@localhost => {
...
    "plugin": "ed25519",
    "authentication_string": "ZIgUREUg5PVgQ6LskhXmO+eZLS0nC8be6HPjYWR4YJY",
...
}
*************************** 2. row ***************************
CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)): edtest2@localhost => {
...
    "plugin": "mysql_native_password",
    "authentication_string": "*14E65567ABDB5135D0CFD9A70B3032C179A49EE7",
...
}

The behavior of this function is affected by the value of the old_passwords system variable. If this is set to 1 (0 is default), MariaDB reverts to using the mysql_old_password authentication plugin by default for newly created users and passwords.

Examples

SELECT PASSWORD('notagoodpwd');
+-------------------------------------------+
| PASSWORD('notagoodpwd')                   |
+-------------------------------------------+
| *3A70EE9FC6594F88CE9E959CD51C5A1C002DC937 |
+-------------------------------------------+
SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

See Also

ENDPOINT

A synonym for ST_ENDPOINT.

GLENGTH

Syntax

GLength(ls)

Description

Returns as a double-precision number the length of the LineString value ls in its associated spatial reference.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT GLength(GeomFromText(@ls));
+----------------------------+
| GLength(GeomFromText(@ls)) |
+----------------------------+
|           2.82842712474619 |
+----------------------------+

See Also

ROLLBACK

The ROLLBACK statement rolls back (ends) a transaction, destroying any changes to SQL-data so that they never become visible to subsequent transactions. The required syntax for the ROLLBACK statement is as follows.

ROLLBACK [ WORK ] [ AND [ NO ] CHAIN ] 
[ TO [ SAVEPOINT ] {<savepoint name> | <simple target specification>} ]

The ROLLBACK statement will either end a transaction, destroying all data changes that happened during any of the transaction, or it will just destroy any data changes that happened since you established a savepoint. The basic form of the ROLLBACK statement is just the keyword ROLLBACK (the keyword WORK is simply noise and can be omitted without changing the effect).

The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated. The AND NO CHAIN option just tells your DBMS to end the transaction that is, these four SQL statements are equivalent:

ROLLBACK; 
ROLLBACK WORK; 
ROLLBACK AND NO CHAIN; 
ROLLBACK WORK AND NO CHAIN; 

All of them end a transaction without saving any transaction characteristics. The only other options, the equivalent statements:

ROLLBACK AND CHAIN;
ROLLBACK WORK AND CHAIN;

both tell your DBMS to end a transaction, but to save that transaction's characteristics for the next transaction.

ROLLBACK is much simpler than COMMIT: it may involve no more than a few deletions (of Cursors, locks, prepared SQL statements and log-file entries). It's usually assumed that ROLLBACK can't fail, although such a thing is conceivable (for example, an encompassing transaction might reject an attempt to ROLLBACK because it's lining up for a COMMIT).

ROLLBACK cancels all effects of a transaction. It does not cancel effects on objects outside the DBMS's control (for example the values in host program variables or the settings made by some SQL/CLI function calls). But in general, it is a convenient statement for those situations when you say "oops, this isn't working" or when you simply don't care whether your temporary work becomes permanent or not.

Here is a moot question. If all you've been doing is SELECTs, so that there have been no data changes, should you end the transaction with ROLLBACK or COMMIT? It shouldn't really matter because both ROLLBACK and COMMIT do the same transaction-terminating job. However, the popular conception is that ROLLBACK implies failure, so after a successful series of SELECT statements the convention is to end the transaction with COMMIT rather than ROLLBACK.

MariaDB (and most other DBMSs) supports rollback of SQL-data change statements, but not of SQL-Schema statements. This means that if you use any of CREATE, ALTER, DROP, GRANT, REVOKE, you are implicitly committing at execution time.

INSERT INTO Table_2 VALUES(5); 
DROP TABLE Table_3 CASCADE; 
ROLLBACK; 

The result will be that both the INSERT and the DROP will go through as separate transactions so the ROLLBACK will have no effect.

NumPoints

A synonym for ST_NumPoints.

PointN

A synonym for ST_PointN.

STARTPOINT

A synonym for ST_STARTPOINT.

ST_ENDPOINT

Syntax

ST_EndPoint(ls)
EndPoint(ls)

Description

Returns the Point that is the endpoint of the LineString value ls.

ST_EndPoint() and EndPoint() are synonyms.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT AsText(EndPoint(GeomFromText(@ls)));
+-------------------------------------+
| AsText(EndPoint(GeomFromText(@ls))) |
+-------------------------------------+
| POINT(3 3)                          |
+-------------------------------------+

ST_NUMPOINTS

Syntax

ST_NumPoints(ls)
NumPoints(ls)

Description

Returns the number of Point objects in the LineString value ls.

ST_NumPoints() and NumPoints() are synonyms.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT NumPoints(GeomFromText(@ls));
+------------------------------+
| NumPoints(GeomFromText(@ls)) |
+------------------------------+
|                            3 |
+------------------------------+

ST_POINTN

Syntax

ST_PointN(ls,N)
PointN(ls,N)

Description

Returns the N-th Point in the LineString value ls. Points are numbered beginning with 1.

ST_PointN() and PointN() are synonyms.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT AsText(PointN(GeomFromText(@ls),2));
+-------------------------------------+
| AsText(PointN(GeomFromText(@ls),2)) |
+-------------------------------------+
| POINT(2 2)                          |
+-------------------------------------+

PREPARE Statement

Syntax

PREPARE stmt_name FROM preparable_stmt

Description

The PREPARE statement prepares a statement and assigns it a name, stmt_name, by which to refer to the statement later. Statement names are not case sensitive. preparable_stmt is either a string literal or a user variable (not a local variable, an SQL expression or a subquery) that contains the text of the statement. The text must represent a single SQL statement, not multiple statements. Within the statement, "?" characters can be used as parameter markers to indicate where data values are to be bound to the query later when you execute it. The "?" characters should not be enclosed within quotes, even if you intend to bind them to string values. Parameter markers can be used only where expressions should appear, not for SQL keywords, identifiers, and so forth.

The scope of a prepared statement is the session within which it is created. Other sessions cannot see it.

If a prepared statement with the given name already exists, it is deallocated implicitly before the new statement is prepared. This means that if the new statement contains an error and cannot be prepared, an error is returned and no statement with the given name exists.

Prepared statements can be PREPAREd and EXECUTEd in a stored procedure, but not in a stored function or trigger. Also, even if the statement is PREPAREd in a procedure, it will not be deallocated when the procedure execution ends.

A prepared statement can access user-defined variables, but not local variables or procedure's parameters.

If the prepared statement contains a syntax error, PREPARE will fail. As a side effect, stored procedures can use it to check if a statement is valid. For example:

CREATE PROCEDURE `test_stmt`(IN sql_text TEXT)
BEGIN
        DECLARE EXIT HANDLER FOR SQLEXCEPTION
        BEGIN
                SELECT CONCAT(sql_text, ' is not valid');
        END;
        SET @SQL := sql_text;
        PREPARE stmt FROM @SQL;
        DEALLOCATE PREPARE stmt;
END;

The FOUND_ROWS() and ROW_COUNT() functions, if called immediatly after EXECUTE, return the number of rows read or affected by the prepared statements; however, if they are called after DEALLOCATE PREPARE, they provide information about this statement. If the prepared statement produces errors or warnings, GET DIAGNOSTICS return information about them. DEALLOCATE PREPARE shouldn't clear the diagnostics area, unless it produces an error.

A prepared statement is executed with EXECUTE and released with DEALLOCATE PREPARE.

The max_prepared_stmt_count server system variable determines the number of allowed prepared statements that can be prepared on the server. If it is set to 0, prepared statements are not allowed. If the limit is reached, an error similar to the following will be produced:

ERROR 1461 (42000): Can't create more than max_prepared_stmt_count statements 
  (current value: 0)

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, PREPARE stmt FROM 'SELECT :1, :2' is used, instead of ?.

Permitted Statements

Not all statements can be prepared. Only the following SQL commands are permitted:

Synonyms are not listed here, but can be used. For example, DESC can be used instead of DESCRIBE.

MariaDB starting with 10.1.1

Compound statements can be prepared too.

Note that if a statement can be run in a stored routine, it will work even if it is called by a prepared statement. For example, SIGNAL can't be directly prepared. However, it is allowed in stored routines. If the x() procedure contains SIGNAL, you can still prepare and execute the 'CALL x();' prepared statement.

MariaDB starting with 10.2.3

PREPARE now supports most kinds of expressions as well, for example:

PREPARE stmt FROM CONCAT('SELECT * FROM ', table_name);
MariaDB starting with 10.6.2

All statements can be prepared, except PREPARE, EXECUTE, and DEALLOCATE / DROP PREPARE.

When PREPARE is used with a statement which is not supported, the following error is produced:

ERROR 1295 (HY000): This command is not supported in the prepared statement protocol yet

Example

create table t1 (a int,b char(10));
insert into t1 values (1,"one"),(2, "two"),(3,"three");
prepare test from "select * from t1 where a=?";
set @param=2;
execute test using @param;
+------+------+
| a    | b    |
+------+------+
|    2 | two  |
+------+------+
set @param=3;
execute test using @param;
+------+-------+
| a    | b     |
+------+-------+
|    3 | three |
+------+-------+
deallocate prepare test;

Since identifiers are not permitted as prepared statements parameters, sometimes it is necessary to dynamically compose an SQL statement. This technique is called dynamic SQL). The following example shows how to use dynamic SQL:

CREATE PROCEDURE test.stmt_test(IN tab_name VARCHAR(64))
BEGIN
	SET @sql = CONCAT('SELECT COUNT(*) FROM ', tab_name);
	PREPARE stmt FROM @sql;
	EXECUTE stmt;
	DEALLOCATE PREPARE stmt;
END;

CALL test.stmt_test('mysql.user');
+----------+
| COUNT(*) |
+----------+
|        4 |
+----------+

Use of variables in prepared statements:

PREPARE stmt FROM 'SELECT @x;';

SET @x = 1;

EXECUTE stmt;
+------+
| @x   |
+------+
|    1 |
+------+

SET @x = 0;

EXECUTE stmt;
+------+
| @x   |
+------+
|    0 |
+------+

DEALLOCATE PREPARE stmt;

See Also

INET_ATON

Syntax

INET_ATON(expr)

Description

Given the dotted-quad representation of an IPv4 network address as a string, returns an integer that represents the numeric value of the address. Addresses may be 4- or 8-byte addresses.

Returns NULL if the argument is not understood.

Examples

SELECT INET_ATON('192.168.1.1');
+--------------------------+
| INET_ATON('192.168.1.1') |
+--------------------------+
|               3232235777 |
+--------------------------+

This is calculated as follows: 192 x 2563 + 168 x 256 2 + 1 x 256 + 1

See Also

INET_NTOA

Syntax

INET_NTOA(expr)

Description

Given a numeric IPv4 network address in network byte order (4 or 8 byte), returns the dotted-quad representation of the address as a string.

Examples

SELECT INET_NTOA(3232235777);
+-----------------------+
| INET_NTOA(3232235777) |
+-----------------------+
| 192.168.1.1           |
+-----------------------+

192.168.1.1 corresponds to 3232235777 since 192 x 2563 + 168 x 256 2 + 1 x 256 + 1 = 3232235777

See Also

IS_FREE_LOCK

Syntax

IS_FREE_LOCK(str)

Description

Checks whether the lock named str is free to use (that is, not locked). Returns 1 if the lock is free (no one is using the lock), 0 if the lock is in use, and NULL if an error occurs (such as an incorrect argument, like an empty string or NULL). str is case insensitive.

If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table contains information about locks of this kind (as well as metadata locks).

Statements using the IS_FREE_LOCK function are not safe for statement-based replication.

See Also

START TRANSACTION

Syntax

START TRANSACTION [transaction_property [, transaction_property] ...] | BEGIN [WORK]
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
SET autocommit = {0 | 1}

transaction_property:
    WITH CONSISTENT SNAPSHOT
  | READ WRITE
  | READ ONLY

Description

The START TRANSACTION or BEGIN statement begins a new transaction. COMMIT commits the current transaction, making its changes permanent. ROLLBACK rolls back the current transaction, canceling its changes. The SET autocommit statement disables or enables the default autocommit mode for the current session.

START TRANSACTION and SET autocommit = 1 implicitly commit the current transaction, if any.

The optional WORK keyword is supported for COMMIT and ROLLBACK, as are the CHAIN and RELEASE clauses. CHAIN and RELEASE can be used for additional control over transaction completion. The value of the completion_type system variable determines the default completion behavior.

The AND CHAIN clause causes a new transaction to begin as soon as the current one ends, and the new transaction has the same isolation level as the just-terminated transaction. The RELEASE clause causes the server to disconnect the current client session after terminating the current transaction. Including the NO keyword suppresses CHAIN or RELEASE completion, which can be useful if the completion_type system variable is set to cause chaining or release completion by default.

Access Mode

The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables.

It is not permitted to specify both READ WRITE and READ ONLY in the same statement.

READ WRITE and READ ONLY can also be specified in the SET TRANSACTION statement, in which case the specified mode is valid for all sessions, or for all subsequent transaction used by the current session.

autocommit

By default, MariaDB runs with autocommit mode enabled. This means that as soon as you execute a statement that updates (modifies) a table, MariaDB stores the update on disk to make it permanent. To disable autocommit mode, use the following statement:

SET autocommit=0;

After disabling autocommit mode by setting the autocommit variable to zero, changes to transaction-safe tables (such as those for InnoDB or NDBCLUSTER) are not made permanent immediately. You must use COMMIT to store your changes to disk or ROLLBACK to ignore the changes.

To disable autocommit mode for a single series of statements, use the START TRANSACTION statement.

DDL Statements

DDL statements (CREATE, ALTER, DROP) and administrative statements (FLUSH, RESET, OPTIMIZE, ANALYZE, CHECK, REPAIR, CACHE INDEX), transaction management statements (BEGIN, START TRANSACTION) and LOAD DATA INFILE, cause an implicit COMMIT and start a new transaction. An exception to this rule are the DDL that operate on temporary tables: you can CREATE, ALTER and DROP them without causing any COMMIT, but those actions cannot be rolled back. This means that if you call ROLLBACK, the temporary tables you created in the transaction will remain, while the rest of the transaction will be rolled back.

Transactions cannot be used in Stored Functions or Triggers. In Stored Procedures and Events BEGIN is not allowed, so you should use START TRANSACTION instead.

A transaction acquires a metadata lock on every table it accesses to prevent other connections from altering their structure. The lock is released at the end of the transaction. This happens even with non-transactional storage engines (like MEMORY or CONNECT), so it makes sense to use transactions with non-transactional tables.

in_transaction

The in_transaction system variable is a session-only, read-only variable that returns 1 inside a transaction, and 0 if not in a transaction.

WITH CONSISTENT SNAPSHOT

The WITH CONSISTENT SNAPSHOT option starts a consistent read for storage engines such as InnoDB that can do so, the same as if a START TRANSACTION followed by a SELECT from any InnoDB table was issued.

See Enhancements for START TRANSACTION WITH CONSISTENT SNAPSHOT.

Examples

START TRANSACTION;
SELECT @A:=SUM(salary) FROM table1 WHERE type=1;
UPDATE table2 SET summary=@A WHERE type=1;
COMMIT;

See Also

IS_IPV6

Syntax

IS_IPV6(expr)

Description

Returns 1 if the expression is a valid IPv6 address specified as a string, otherwise returns 0. Does not consider IPv4 addresses to be valid IPv6 addresses.

Examples

 SELECT IS_IPV6('48f3::d432:1431:ba23:846f');
+--------------------------------------+
| IS_IPV6('48f3::d432:1431:ba23:846f') |
+--------------------------------------+
|                                    1 |
+--------------------------------------+
1 row in set (0.02 sec)

SELECT IS_IPV6('10.0.1.1');
+---------------------+
| IS_IPV6('10.0.1.1') |
+---------------------+
|                   0 |
+---------------------+

See Also

Transaction Timeouts

MariaDB has always had the wait_timeout and interactive_timeout settings, which close connections after a certain period of inactivity.

However, these are by default set to a long wait period. In situations where transactions may be started, but not committed or rolled back, more granular control and a shorter timeout may be desirable so as to avoid locks being held for too long.

MariaDB 10.3 introduced three new variables to handle this situation.

These accept a time in seconds to time out, by closing the connection, transactions that are idle for longer than this period. By default all are set to zero, or no timeout.

idle_transaction_timeout affects all transactions, idle_write_transaction_timeout affects write transactions only and idle_readonly_transaction_timeout affects read transactions only. The latter two variables work independently. However, if either is set along with idle_transaction_timeout, the settings for idle_write_transaction_timeout or idle_readonly_transaction_timeout will take precedence.

Examples

SET SESSION idle_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away
SET SESSION idle_write_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
INSERT INTO t VALUES(1);
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away
SET SESSION idle_transaction_timeout=2, SESSION idle_readonly_transaction_timeout=10;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
 ## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
## wait 11 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away

WAIT and NOWAIT

MariaDB starting with 10.3.0

MariaDB 10.3.0 introduced extended syntax so that it is possible to set innodb_lock_wait_timeout and lock_wait_timeout for the following statements:

Syntax

ALTER TABLE tbl_name [WAIT n|NOWAIT] ...
CREATE ... INDEX ON tbl_name (index_col_name, ...) [WAIT n|NOWAIT] ...
DROP INDEX ... [WAIT n|NOWAIT]
DROP TABLE tbl_name [WAIT n|NOWAIT] ...
LOCK TABLE ... [WAIT n|NOWAIT]
OPTIMIZE TABLE tbl_name [WAIT n|NOWAIT]
RENAME TABLE tbl_name [WAIT n|NOWAIT] ...
SELECT ... FOR UPDATE [WAIT n|NOWAIT]
SELECT ... LOCK IN SHARE MODE [WAIT n|NOWAIT]
TRUNCATE TABLE tbl_name [WAIT n|NOWAIT]

Description

The lock wait timeout can be explicitly set in the statement by using either WAIT n (to set the wait in seconds) or NOWAIT, in which case the statement will immediately fail if the lock cannot be obtained. WAIT 0 is equivalent to NOWAIT.

See Also

Account Locking

MariaDB starting with 10.4.2

Account locking was introduced in MariaDB 10.4.2.

Description

Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected).

User accounts can be locked at creation, with the CREATE USER statement, or modified after creation with the ALTER USER statement. For example:

CREATE USER 'lorin'@'localhost' ACCOUNT LOCK;

or

ALTER USER 'marijn'@'localhost' ACCOUNT LOCK;

The server will return an ER_ACCOUNT_HAS_BEEN_LOCKED error when locked users attempt to connect:

mysql -ulorin
  ERROR 4151 (HY000): Access denied, this account is locked

The ALTER USER statement is also used to unlock a user:

ALTER USER 'lorin'@'localhost' ACCOUNT UNLOCK;

The SHOW CREATE USER statement will show whether the account is locked:

SHOW CREATE USER 'marijn'@'localhost';
+-----------------------------------------------+
| CREATE USER for marijn@localhost              |
+-----------------------------------------------+
| CREATE USER 'marijn'@'localhost' ACCOUNT LOCK |
+-----------------------------------------------+

as well as querying the mysql.global_priv table:

SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv 
  WHERE user='marijn';
+--------------------------------------------------------------------------------------+
| CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv))                                 |
+--------------------------------------------------------------------------------------+
| marijn@localhost => {
    "access": 0,
    "plugin": "mysql_native_password",
    "authentication_string": "",
    "account_locked": true,
    "password_last_changed": 1558017158
} |
+--------------------------------------------------------------------------------------+

See Also

IS_USED_LOCK

Syntax

IS_USED_LOCK(str)

Description

Checks whether the lock named str is in use (that is, locked). If so, it returns the connection identifier of the client that holds the lock. Otherwise, it returns NULL. str is case insensitive.

If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table contains information about locks of this kind (as well as metadata locks).

Statements using the IS_USED_LOCK function are not safe for statement-based replication.

See Also

User Password Expiry

MariaDB starting with 10.4.3

User password expiry was introduced in MariaDB 10.4.3.

Password expiry permits administrators to expire user passwords, either manually or automatically.

System Variables

There are two system variables which affect password expiry: default_password_lifetime, which determines the amount of time between requiring the user to change their password. 0, the default, means automatic password expiry is not active.

The second variable, disconnect_on_expired_password determines whether a client is permitted to connect if their password has expired, or whether they are permitted to connect in sandbox mode, able to perform a limited subset of queries related to resetting the password, in particular SET PASSWORD and SET.

Setting a Password Expiry Limit for a User

Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global using the CREATE USER or ALTER USER statements, for example:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;

Limits can be disabled by use of the NEVER keyword, for example:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;

A manually set limit can be restored the system default by use of DEFAULT, for example:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;

SHOW CREATE USER

The SHOW CREATE USER statement will display information about the password expiry status of the user. Unlike MySQL, it will not display if the user is unlocked, or if the password expiry is set to default.

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;
CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE NEVER;
CREATE USER 'amse'@'localhost' PASSWORD EXPIRE DEFAULT;

SHOW CREATE USER 'monty'@'localhost';
+------------------------------------------------------------------+
| CREATE USER for monty@localhost                                  |
+------------------------------------------------------------------+
| CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY |
+------------------------------------------------------------------+

SHOW CREATE USER 'konstantin'@'localhost';
+------------------------------------------------------------+
| CREATE USER for konstantin@localhost                       |
+------------------------------------------------------------+
| CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE NEVER |
+------------------------------------------------------------+

SHOW CREATE USER 'amse'@'localhost';
+--------------------------------+
| CREATE USER for amse@localhost |
+--------------------------------+
| CREATE USER 'amse'@'localhost' |
+--------------------------------+

Checking When Passwords Expire

The following query can be used to check when the current passwords expire for all users:

WITH password_expiration_info AS (
  SELECT User, Host,
  IF(
   IFNULL(JSON_EXTRACT(Priv, '$.password_lifetime'), -1) = -1,
   @@global.default_password_lifetime,
   JSON_EXTRACT(Priv, '$.password_lifetime')
  ) AS password_lifetime,
  JSON_EXTRACT(Priv, '$.password_last_changed') AS password_last_changed
  FROM mysql.global_priv
)
SELECT pei.User, pei.Host,
  pei.password_lifetime,
  FROM_UNIXTIME(pei.password_last_changed) AS password_last_changed_datetime,
  FROM_UNIXTIME(
   pei.password_last_changed +
   (pei.password_lifetime * 60 * 60 * 24)
  ) AS password_expiration_datetime
  FROM password_expiration_info pei
  WHERE pei.password_lifetime != 0
   AND pei.password_last_changed IS NOT NULL
UNION
SELECT pei.User, pei.Host,
  pei.password_lifetime,
  FROM_UNIXTIME(pei.password_last_changed) AS password_last_changed_datetime,
  0 AS password_expiration_datetime
  FROM password_expiration_info pei
  WHERE pei.password_lifetime = 0
   OR pei.password_last_changed IS NULL;

--connect-expired-password Client Option

The mysql client --connect-expired-password option notifies the server that the client is prepared to handle expired password sandbox mode (even if the --batch option was specified).

See Also

NAME_CONST

Syntax

NAME_CONST(name,value)

Description

Returns the given value. When used to produce a result set column, NAME_CONST() causes the column to have the given name. The arguments should be constants.

This function is used internally when replicating stored procedures. It makes little sense to use it explicitly in SQL statements, and it was not supposed to be used like that.

SELECT NAME_CONST('myname', 14);
+--------+
| myname |
+--------+
|     14 |
+--------+

SLEEP

Syntax

SLEEP(duration)

Description

Sleeps (pauses) for the number of seconds given by the duration argument, then returns 0. If SLEEP() is interrupted, it returns 1. The duration may have a fractional part given in microseconds.

Statements using the SLEEP() function are not safe for replication.

Example

SELECT SLEEP(5.5);
+------------+
| SLEEP(5.5) |
+------------+
|          0 |
+------------+
1 row in set (5.50 sec)

UUID_SHORT

Syntax

UUID_SHORT()

Description

Returns a "short" universally unique identifier as a 64-bit unsigned integer (rather than a string-form 128-bit identifier as returned by the UUID() function).

The value of UUID_SHORT() is guaranteed to be unique if the following conditions hold:

  • The server_id of the current host is unique among your set of master and slave servers
  • server_id is between 0 and 255
  • You don't set back your system time for your server between mysqld restarts
  • You do not invoke UUID_SHORT() on average more than 16 million times per second between mysqld restarts

The UUID_SHORT() return value is constructed this way:

  (server_id & 255) << 56
+ (server_startup_time_in_seconds << 24)
+ incremented_variable++;

Statements using the UUID_SHORT() function are not safe for statement-based replication.

Examples

SELECT UUID_SHORT();
+-------------------+
| UUID_SHORT()      |
+-------------------+
| 21517162376069120 |
+-------------------+
create table t1 (a bigint unsigned default(uuid_short()) primary key);
insert into t1 values(),();
select * from t1;
+-------------------+
| a                 |
+-------------------+
| 98113699159474176 |
| 98113699159474177 |
+-------------------+

See Also

!

Syntax

NOT, !

Description

Logical NOT. Evaluates to 1 if the operand is 0, to 0 if the operand is non-zero, and NOT NULL returns NULL.

By default, the ! operator has a higher precedence. If the HIGH_NOT_PRECEDENCE SQL_MODE flag is set, NOT and ! have the same precedence.

Examples

SELECT NOT 10;
+--------+
| NOT 10 |
+--------+
|      0 |
+--------+

SELECT NOT 0;
+-------+
| NOT 0 |
+-------+
|     1 |
+-------+

SELECT NOT NULL;
+----------+
| NOT NULL |
+----------+
|     NULL |
+----------+

SELECT ! (1+1);
+---------+
| ! (1+1) |
+---------+
|       0 |
+---------+

SELECT ! 1+1;
+-------+
| ! 1+1 |
+-------+
|     1 |
+-------+

&&

Syntax

AND, &&

Description

Logical AND. Evaluates to 1 if all operands are non-zero and not NULL, to 0 if one or more operands are 0, otherwise NULL is returned.

For this operator, short-circuit evaluation can be used.

Examples

SELECT 1 && 1;
+--------+
| 1 && 1 |
+--------+
|      1 |
+--------+

SELECT 1 && 0;
+--------+
| 1 && 0 |
+--------+
|      0 |
+--------+

SELECT 1 && NULL;
+-----------+
| 1 && NULL |
+-----------+
|      NULL |
+-----------+

SELECT 0 && NULL;
+-----------+
| 0 && NULL |
+-----------+
|         0 |
+-----------+

SELECT NULL && 0;
+-----------+
| NULL && 0 |
+-----------+
|         0 |
+-----------+

Assignment Operator (:=)

Syntax

var_name := expr

Description

Assignment operator for assigning a value. The value on the right is assigned to the variable on left.

Unlike the = operator, := can always be used to assign a value to a variable.

This operator works with both user-defined variables and local variables.

When assigning the same value to several variables, LAST_VALUE() can be useful.

Examples

 SELECT @x := 10;
+----------+
| @x := 10 |
+----------+
|       10 |
+----------+

SELECT @x, @y := @x;
+------+----------+
| @x   | @y := @x |
+------+----------+
|   10 |       10 |
+------+----------+

GROUP_CONCAT

Syntax

GROUP_CONCAT(expr)

Description

This function returns a string result with the concatenated non-NULL values from a group. It returns NULL if there are no non-NULL values.

The maximum returned length in bytes is determined by the group_concat_max_len server system variable, which defaults to 1M (>= MariaDB 10.2.4) or 1K (<= MariaDB 10.2.3).

If group_concat_max_len <= 512, the return type is VARBINARY or VARCHAR; otherwise, the return type is BLOB or TEXT. The choice between binary or non-binary types depends from the input.

The full syntax is as follows:

GROUP_CONCAT([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [SEPARATOR str_val]
             [LIMIT {[offset,] row_count | row_count OFFSET offset}])

DISTINCT eliminates duplicate values from the output string.

ORDER BY determines the order of returned values.

SEPARATOR specifies a separator between the values. The default separator is a comma (,). It is possible to avoid using a separator by specifying an empty string.

LIMIT

MariaDB starting with 10.3.3

Until MariaDB 10.3.2, it was not possible to use the LIMIT clause with GROUP_CONCAT. This restriction was lifted in MariaDB 10.3.3.

Examples

SELECT student_name,
       GROUP_CONCAT(test_score)
       FROM student
       GROUP BY student_name;

Get a readable list of MariaDB users from the mysql.user table:

SELECT GROUP_CONCAT(DISTINCT User ORDER BY User SEPARATOR '\n')
   FROM mysql.user;

In the former example, DISTINCT is used because the same user may occur more than once. The new line (\n) used as a SEPARATOR makes the results easier to read.

Get a readable list of hosts from which each user can connect:

SELECT User, GROUP_CONCAT(Host ORDER BY Host SEPARATOR ', ') 
   FROM mysql.user GROUP BY User ORDER BY User;

The former example shows the difference between the GROUP_CONCAT's ORDER BY (which sorts the concatenated hosts), and the SELECT's ORDER BY (which sorts the rows).

From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT, so, for example, given the following table:

CREATE TABLE d (dd DATE, cc INT);

INSERT INTO d VALUES ('2017-01-01',1);
INSERT INTO d VALUES ('2017-01-02',2);
INSERT INTO d VALUES ('2017-01-04',3);

the following query:

SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) FROM d;
+----------------------------------------------------------------------------+
| SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) |
+----------------------------------------------------------------------------+
| 2017-01-04:3                                                               |
+----------------------------------------------------------------------------+

can be more simply rewritten as:

SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) FROM d;
+-------------------------------------------------------------+
| GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) |
+-------------------------------------------------------------+
| 2017-01-04:3                                                |
+-------------------------------------------------------------+

See Also

STDDEV_SAMP

Syntax

STDDEV_SAMP(expr)

Description

Returns the sample standard deviation of expr (the square root of VAR_SAMP()).

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV_SAMP() can be used as a window function.

STDDEV_SAMP() returns NULL if there were no matching rows.

BENCHMARK

Syntax

BENCHMARK(count,expr)

Description

The BENCHMARK() function executes the expression expr repeatedly count times. It may be used to time how quickly MariaDB processes the expression. The result value is always 0. The intended use is from within the mysql client, which reports query execution times.

Examples

SELECT BENCHMARK(1000000,ENCODE('hello','goodbye'));
+----------------------------------------------+
| BENCHMARK(1000000,ENCODE('hello','goodbye')) |
+----------------------------------------------+
|                                            0 |
+----------------------------------------------+
1 row in set (0.21 sec)

Roles Overview

MariaDB starting with 10.0.5

Roles were introduced in MariaDB 10.0.5.

Description

A role bundles a number of privileges together. It assists larger organizations where, typically, a number of users would have the same privileges, and, previously, the only way to change the privileges for a group of users was by changing each user's privileges individually.

Alternatively, multiple external users could have been assigned the same user, and there would have been no way to see which actual user was responsible for which action.

With roles, managing this is easy. For example, there could be a number of users assigned to a journalist role, with identical privileges. Changing the privileges for all the journalists is a matter of simply changing the role's privileges, while the individual user is still linked with any changes that take place.

Roles are created with the CREATE ROLE statement, and dropped with the DROP ROLE statement. Roles are then assigned to a user with an extension to the GRANT statement, while privileges are assigned to a role in the regular way with GRANT. Similarly, the REVOKE statement can be used to both revoke a role from a user, or revoke a privilege from a role.

Once a user has connected, he can obtain all privileges associated with a role by setting a role with the SET ROLE statement. The CURRENT_ROLE function returns the currently set role for the session, if any.

Only roles granted directly to a user can be set, roles granted to other roles cannot. Instead the privileges granted to a role, which is, in turn, granted to another role (grantee), will be immediately available to any user who sets this second grantee role.

Roles were implemented as a GSoC 2013 project by Vicentiu Ciorbaru.

MariaDB starting with 10.1.1

The SET DEFAULT ROLE statement allows one to set a default role for a user. A default role is automatically enabled when a user connects (an implicit SET ROLE statement is executed immediately after a connection is established).

System Tables

Information about roles and who they've been granted to can be found in the Information Schema APPLICABLE_ROLES table as well as the mysql.ROLES_MAPPING table.

The Information Schema ENABLED_ROLES table shows the enabled roles for the current session.

Examples

Creating a role and granting a privilege:

CREATE ROLE journalist;

GRANT SHOW DATABASES ON *.* TO journalist;

GRANT journalist to hulda;

Note, that hulda has no SHOW DATABASES privilege, even though she was granted the journalist role. She needs to set the role first:

SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE journalist;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| journalist   |
+--------------+

SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| ...                |
| information_schema |
| mysql              |
| performance_schema |
| test               |
| ...                |
+--------------------+

SET ROLE NONE;

Roles can be granted to roles:

CREATE ROLE writer;

GRANT SELECT ON data.* TO writer;

GRANT writer TO journalist;

But one does not need to set a role granted to a role. For example, hulda will automatically get all writer privileges when she sets the journalist role:

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SHOW TABLES FROM data;
Empty set (0.01 sec)

SET ROLE journalist;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| journalist   |
+--------------+

SHOW TABLES FROM data;
+------------------------------+
| Tables_in_data               |
+------------------------------+
| set1                         |
| ...                          |
+------------------------------+

Roles and Views (and Stored Routines)

When a user sets a role, he, in a sense, has two identities with two associated sets of privileges. But a view (or a stored routine) can have only one definer. So, when a view (or a stored routine) is created with the SQL SECURITY DEFINER, one can specify whether the definer should be CURRENT_USER (and the view will have none of the privileges of the user's role) or CURRENT_ROLE (in this case, the view will use role's privileges, but none of the user's privileges). As a result, sometimes one can create a view that is impossible to use.

CREATE ROLE r1;

GRANT ALL ON db1.* TO r1;

GRANT r1 TO foo@localhost;

GRANT ALL ON db.* TO foo@localhost;

SELECT CURRENT_USER
+---------------+
| current_user  |
+---------------+
| foo@localhost |
+---------------+

SET ROLE r1;

CREATE TABLE db1.t1 (i int);

CREATE VIEW db.v1 AS SELECT * FROM db1.t1;

SHOW CREATE VIEW db.v1;
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View                                                                                                                              | character_set_client | collation_connection |
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| v1   | CREATE ALGORITHM=UNDEFINED DEFINER=`foo`@`localhost` SQL SECURITY DEFINER VIEW `db`.`v1` AS SELECT `db1`.`t1`.`i` AS `i` from `db1`.`t1` | utf8                 | utf8_general_ci      |
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+

CREATE DEFINER=CURRENT_ROLE VIEW db.v2 AS SELECT * FROM db1.t1;

SHOW CREATE VIEW db.b2;
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View                                                                                                                 | character_set_client | collation_connection |
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| v2   | CREATE ALGORITHM=UNDEFINED DEFINER=`r1` SQL SECURITY DEFINER VIEW `db`.`v2` AS select `db1`.`t1`.`a` AS `a` from `db1`.`t1` | utf8                 | utf8_general_ci      |
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+

Other Resources

BINLOG_GTID_POS

Syntax

BINLOG_GTID_POS(binlog_filename,binlog_offset)

Description

The BINLOG_GTID_POS() function takes as input an old-style binary log position in the form of a file name and a file offset. It looks up the position in the current binlog, and returns a string representation of the corresponding GTID position. If the position is not found in the current binlog, NULL is returned.

Examples

SELECT BINLOG_GTID_POS("master-bin.000001", 600);

See Also

COLLATION

Syntax

COLLATION(str)

Description

Returns the collation of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set.

See Character Sets and Collations.

Examples

SELECT COLLATION('abc');
+-------------------+
| COLLATION('abc')  |
+-------------------+
| latin1_swedish_ci |
+-------------------+

SELECT COLLATION(_utf8'abc');
+-----------------------+
| COLLATION(_utf8'abc') |
+-----------------------+
| utf8_general_ci       |
+-----------------------+

See Also

AES_ENCRYPT

Syntax

AES_ENCRYPT(str,key_str)

Description

AES_ENCRYPT() and AES_DECRYPT() allow encryption and decryption of data using the official AES (Advanced Encryption Standard) algorithm, previously known as "Rijndael." Encoding with a 128-bit key length is used, but you can extend it up to 256 bits by modifying the source. We chose 128 bits because it is much faster and it is secure enough for most purposes.

AES_ENCRYPT() encrypts a string str using the key key_str, and returns a binary string.

AES_DECRYPT() decrypts the encrypted string and returns the original string.

The input arguments may be any length. If either argument is NULL, the result of this function is also NULL.

Because AES is a block-level algorithm, padding is used to encode uneven length strings and so the result string length may be calculated using this formula:

16 x (trunc(string_length / 16) + 1)

If AES_DECRYPT() detects invalid data or incorrect padding, it returns NULL. However, it is possible for AES_DECRYPT() to return a non-NULL value (possibly garbage) if the input data or the key is invalid.

Examples

INSERT INTO t VALUES (AES_ENCRYPT('text',SHA2('password',512)));

COMPRESS

Syntax

COMPRESS(string_to_compress)

Description

Compresses a string and returns the result as a binary string. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The compressed string can be uncompressed with UNCOMPRESS().

The have_compress server system variable indicates whether a compression library is present.

Examples

SELECT LENGTH(COMPRESS(REPEAT('a',1000)));
+------------------------------------+
| LENGTH(COMPRESS(REPEAT('a',1000))) |
+------------------------------------+
|                                 21 |
+------------------------------------+

SELECT LENGTH(COMPRESS(''));
+----------------------+
| LENGTH(COMPRESS('')) |
+----------------------+
|                    0 |
+----------------------+

SELECT LENGTH(COMPRESS('a'));
+-----------------------+
| LENGTH(COMPRESS('a')) |
+-----------------------+
|                    13 |
+-----------------------+

SELECT LENGTH(COMPRESS(REPEAT('a',16)));
+----------------------------------+
| LENGTH(COMPRESS(REPEAT('a',16))) |
+----------------------------------+
|                               15 |
+----------------------------------+

CONNECTION_ID

Syntax

CONNECTION_ID()

Description

Returns the connection ID (thread ID) for the connection. Every thread (including events) has an ID that is unique among the set of currently connected clients.

Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits.

Examples

SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
|               3 |
+-----------------+

See Also

SCHEMA

Syntax

SCHEMA()

Description

This function is a synonym for DATABASE().

SESSION_USER

Syntax

SESSION_USER()

Description

SESSION_USER() is a synonym for USER().

SYSTEM_USER

Syntax

SYSTEM_USER()

Description

SYSTEM_USER() is a synonym for USER().

<

Syntax

<

Description

Less than operator. Evaluates both SQL expressions and returns 1 if the left value is less than the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) < (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a < t2.x) OR ((t1.a = t2.x) AND (t1.b < t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 < 2;
+-------+
| 2 < 2 |
+-------+
|     0 |
+-------+

Type conversion:

SELECT 3<'4';
+-------+
| 3<'4' |
+-------+
|     1 |
+-------+

Case insensitivity - see Character Sets and Collations:

SELECT 'a'<'A';
+---------+
| 'a'<'A' |
+---------+
|       0 |
+---------+

<=

Syntax

<=

Description

Less than or equal operator. Evaluates both SQL expressions and returns 1 if the left value is less than or equal to the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) <= (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a < t2.x) OR ((t1.a = t2.x) AND (t1.b <= t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 0.1 <= 2;
+----------+
| 0.1 <= 2 |
+----------+
|        1 |
+----------+
SELECT 'a'<='A';
+----------+
| 'a'<='A' |
+----------+
|        1 |
+----------+

BETWEEN AND

Syntax

expr BETWEEN min AND max

Description

If expr is greater than or equal to min and expr is less than or equal to max, BETWEEN returns 1, otherwise it returns 0. This is equivalent to the expression (min <= expr AND expr <= max) if all the arguments are of the same type. Otherwise type conversion takes place according to the rules described at Type Conversion, but applied to all the three arguments.

Examples

SELECT 1 BETWEEN 2 AND 3;
+-------------------+
| 1 BETWEEN 2 AND 3 |
+-------------------+
|                 0 |
+-------------------+
SELECT 'b' BETWEEN 'a' AND 'c';
+-------------------------+
| 'b' BETWEEN 'a' AND 'c' |
+-------------------------+
|                       1 |
+-------------------------+
SELECT 2 BETWEEN 2 AND '3';
+---------------------+
| 2 BETWEEN 2 AND '3' |
+---------------------+
|                   1 |
+---------------------+
SELECT 2 BETWEEN 2 AND 'x-3';
+-----------------------+
| 2 BETWEEN 2 AND 'x-3' |
+-----------------------+
|                     0 |
+-----------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect DOUBLE value: 'x-3'

NULL:

SELECT 1 BETWEEN 1 AND NULL;
+----------------------+
| 1 BETWEEN 1 AND NULL |
+----------------------+
|                 NULL |
+----------------------+

DATE, DATETIME and TIMESTAMP examples. Omitting the time component compares against 00:00, so later times on the same date are not returned:

CREATE TABLE `x` (
  a date ,
  b datetime,
  c timestamp
)

INSERT INTO x VALUES 
 ('2018-11-11', '2018-11-11 05:15', '2018-11-11 05:15'), 
 ('2018-11-12', '2018-11-12 05:15', '2018-11-12 05:15'); 

SELECT * FROM x WHERE a BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
| 2018-11-12 | 2018-11-12 05:15:00 | 2018-11-12 05:15:00 |
+------------+---------------------+---------------------+

SELECT * FROM x WHERE b BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
+------------+---------------------+---------------------+

SELECT * FROM x WHERE c BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
+------------+---------------------+---------------------+

GREATEST

Syntax

GREATEST(value1,value2,...)

Description

With two or more arguments, returns the largest (maximum-valued) argument. The arguments are compared using the same rules as for LEAST().

Examples

SELECT GREATEST(2,0);
+---------------+
| GREATEST(2,0) |
+---------------+
|             2 |
+---------------+
SELECT GREATEST(34.0,3.0,5.0,767.0);
+------------------------------+
| GREATEST(34.0,3.0,5.0,767.0) |
+------------------------------+
|                        767.0 |
+------------------------------+
SELECT GREATEST('B','A','C');
+-----------------------+
| GREATEST('B','A','C') |
+-----------------------+
| C                     |
+-----------------------+

DES_DECRYPT

Syntax

DES_DECRYPT(crypt_str[,key_str])

Description

Decrypts a string encrypted with DES_ENCRYPT(). If an error occurs, this function returns NULL.

This function works only if MariaDB has been configured with TLS support.

If no key_str argument is given, DES_DECRYPT() examines the first byte of the encrypted string to determine the DES key number that was used to encrypt the original string, and then reads the key from the DES key file to decrypt the message. For this to work, the user must have the SUPER privilege. The key file can be specified with the --des-key-file server option.

If you pass this function a key_str argument, that string is used as the key for decrypting the message.

If the crypt_str argument does not appear to be an encrypted string, MariaDB returns the given crypt_str.

DES_ENCRYPT

Syntax

DES_ENCRYPT(str[,{key_num|key_str}])

Description

Encrypts the string with the given key using the Triple-DES algorithm.

This function works only if MariaDB has been configured with TLS support.

The encryption key to use is chosen based on the second argument to DES_ENCRYPT(), if one was given. With no argument, the first key from the DES key file is used. With a key_num argument, the given key number (0-9) from the DES key file is used. With a key_str argument, the given key string is used to encrypt str.

The key file can be specified with the --des-key-file server option.

The return string is a binary string where the first character is CHAR(128 | key_num). If an error occurs, DES_ENCRYPT() returns NULL.

The 128 is added to make it easier to recognize an encrypted key. If you use a string key, key_num is 127.

The string length for the result is given by this formula:

new_len = orig_len + (8 - (orig_len % 8)) + 1

Each line in the DES key file has the following format:

key_num des_key_str

Each key_num value must be a number in the range from 0 to 9. Lines in the file may be in any order. des_key_str is the string that is used to encrypt the message. There should be at least one space between the number and the key. The first key is the default key that is used if you do not specify any key argument to DES_ENCRYPT().

You can tell MariaDB to read new key values from the key file with the FLUSH DES_KEY_FILE statement. This requires the RELOAD privilege.

One benefit of having a set of default keys is that it gives applications a way to check for the existence of encrypted column values, without giving the end user the right to decrypt those values.

Examples

SELECT customer_address FROM customer_table 
   WHERE crypted_credit_card = DES_ENCRYPT('credit_card_number');

See Also

ENCODE

Syntax

ENCODE(str,pass_str)

Description

ENCODE is not considered cryptographically secure, and should not be used for password encryption.

Encrypt str using pass_str as the password. To decrypt the result, use DECODE().

The result is a binary string of the same length as str.

The strength of the encryption is based on how good the random generator is.

It is not recommended to rely on the encryption performed by the ENCODE function. Using a salt value (changed when a password is updated) will improve matters somewhat, but for storing passwords, consider a more cryptographically secure function, such as SHA2().

Examples

ENCODE('not so secret text', CONCAT('random_salt','password'))

ENCRYPT

Syntax

ENCRYPT(str[,salt])

Description

Encrypts a string using the Unix crypt() system call, returning an encrypted binary string. The salt argument should be a string with at least two characters or the returned result will be NULL. If no salt argument is given, a random value of sufficient length is used.

It is not recommended to use ENCRYPT() with utf16, utf32 or ucs2 multi-byte character sets because the crypt() system call expects a string terminated with a zero byte.

Note that the underlying crypt() system call may have some limitations, such as ignoring all but the first eight characters.

If the have_crypt system variable is set to NO (because the crypt() system call is not available), the ENCRYPT function will always return NULL.

Examples

SELECT ENCRYPT('encrypt me');
+-----------------------+
| ENCRYPT('encrypt me') |
+-----------------------+
| 4I5BsEx0lqTDk         |
+-----------------------+

INTERVAL

Syntax

INTERVAL(N,N1,N2,N3,...)

Description

Returns the index of the last argument that is less than the first argument or is NULL.

Returns 0 if N < N1, 1 if N < N2, 2 if N < N3 and so on or -1 if N is NULL. All arguments are treated as integers. It is required that N1 < N2 < N3 < ... < Nn for this function to work correctly. This is because a fast binary search is used.

Examples

SELECT INTERVAL(23, 1, 15, 17, 30, 44, 200);
+--------------------------------------+
| INTERVAL(23, 1, 15, 17, 30, 44, 200) |
+--------------------------------------+
|                                    3 |
+--------------------------------------+

SELECT INTERVAL(10, 1, 10, 100, 1000);
+--------------------------------+
| INTERVAL(10, 1, 10, 100, 1000) |
+--------------------------------+
|                              2 |
+--------------------------------+

SELECT INTERVAL(22, 23, 30, 44, 200);
+-------------------------------+
| INTERVAL(22, 23, 30, 44, 200) |
+-------------------------------+
|                             0 |
+-------------------------------+

SELECT INTERVAL(10, 2, NULL);
+-----------------------+
| INTERVAL(10, 2, NULL) |
+-----------------------+
|                     2 |
+-----------------------+

IS NOT NULL

Syntax

IS NOT NULL

Description

Tests whether a value is not NULL. See also NULL Values in MariaDB.

Examples

SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
+---------------+---------------+------------------+
| 1 IS NOT NULL | 0 IS NOT NULL | NULL IS NOT NULL |
+---------------+---------------+------------------+
|             1 |             1 |                0 |
+---------------+---------------+------------------+

See also

ISNULL

Syntax

ISNULL(expr)

Description

If expr is NULL, ISNULL() returns 1, otherwise it returns 0.

See also NULL Values in MariaDB.

Examples

SELECT ISNULL(1+1);
+-------------+
| ISNULL(1+1) |
+-------------+
|           0 |
+-------------+

SELECT ISNULL(1/0);
+-------------+
| ISNULL(1/0) |
+-------------+
|           1 |
+-------------+

Operator Precedence

The precedence is the order in which the SQL operators are evaluated.

The following list shows the SQL operator precedence. Operators that appear first in the list have a higher precedence. Operators which are listed together have the same precedence.

Functions precedence is always higher than operators precedence.

In this page CASE refers to the CASE operator, not to the CASE statement.

If the HIGH_NOT_PRECEDENCE SQL_MODE is set, NOT has the same precedence as !.

The || operator's precedence, as well as its meaning, depends on the PIPES_AS_CONCAT SQL_MODE flag: if it is on, || can be used to concatenate strings (like the CONCAT() function) and has a higher precedence.

The = operator's precedence depends on the context - it is higher when = is used as a comparison operator.

Parenthesis can be used to modify the operators precedence in an expression.

Short-circuit evaluation

The AND, OR, && and || operators support short-circuit evaluation. This means that, in some cases, the expression on the right of those operators is not evaluated, because its result cannot affect the result. In the following cases, short-circuit evaluation is used and x() is not evaluated:

  • FALSE AND x()
  • FALSE && x()
  • TRUE OR x()
  • TRUE || x()
  • NULL BETWEEN x() AND x()

Note however that the short-circuit evaluation does not apply to NULL AND x(). Also, BETWEEN's right operands are not evaluated if the left operand is NULL, but in all other cases all the operands are evaluated.

This is a speed optimization. Also, since functions can have side-effects, this behavior can be used to choose whether execute them or not using a concise syntax:

SELECT some_function() OR log_error();

&

Syntax

&

Description

Bitwise AND. Converts the values to binary and compares bits. Only if both the corresponding bits are 1 is the resulting bit also 1.

See also bitwise OR.

Examples

SELECT 2&1;
+-----+
| 2&1 |
+-----+
|   0 |
+-----+

SELECT 3&1;
+-----+
| 3&1 |
+-----+
|   1 |
+-----+

SELECT 29 & 15;
+---------+
| 29 & 15 |
+---------+
|      13 |
+---------+

OLD_PASSWORD

Syntax

OLD_PASSWORD(str)

Description

OLD_PASSWORD() was added to MySQL when the implementation of PASSWORD() was changed to improve security. OLD_PASSWORD() returns the value of the old (pre-MySQL 4.1) implementation of PASSWORD() as a string, and is intended to permit you to reset passwords for any pre-4.1 clients that need to connect to a more recent MySQL server version, or any version of MariaDB, without locking them out.

As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

The return value is 16 bytes in length, or NULL if the argument was NULL.

See Also

SHA1

Syntax

SHA1(str), SHA(str)

Description

Calculates an SHA-1 160-bit checksum for the string str, as described in RFC 3174 (Secure Hash Algorithm).

The value is returned as a string of 40 hex digits, or NULL if the argument was NULL. As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

Examples

SELECT SHA1('some boring text');
+------------------------------------------+
| SHA1('some boring text')                 |
+------------------------------------------+
| af969fc2085b1bb6d31e517d5c456def5cdd7093 |
+------------------------------------------+

SHA2

Syntax

SHA2(str,hash_len)

Description

Given a string str, calculates an SHA-2 checksum, which is considered more cryptographically secure than its SHA-1 equivalent. The SHA-2 family includes SHA-224, SHA-256, SHA-384, and SHA-512, and the hash_len must correspond to one of these, i.e. 224, 256, 384 or 512. 0 is equivalent to 256.

The return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables.

NULL is returned if the hash length is not valid, or the string str is NULL.

SHA2 will only work if MariaDB was has been configured with TLS support.

Examples

SELECT SHA2('Maria',224);
+----------------------------------------------------------+
| SHA2('Maria',224)                                        |
+----------------------------------------------------------+
| 6cc67add32286412efcab9d0e1675a43a5c2ef3cec8879f81516ff83 |
+----------------------------------------------------------+

SELECT SHA2('Maria',256);
+------------------------------------------------------------------+
| SHA2('Maria',256)                                                |
+------------------------------------------------------------------+
| 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 |
+------------------------------------------------------------------+

SELECT SHA2('Maria',0);
+------------------------------------------------------------------+
| SHA2('Maria',0)                                                  |
+------------------------------------------------------------------+
| 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 |
+------------------------------------------------------------------+

UNCOMPRESS

Syntax

UNCOMPRESS(string_to_uncompress)

Description

Uncompresses a string compressed by the COMPRESS() function. If the argument is not a compressed value, the result is NULL. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The have_compress server system variable indicates whether a compression library is present.

Examples

SELECT UNCOMPRESS(COMPRESS('a string'));
+----------------------------------+
| UNCOMPRESS(COMPRESS('a string')) |
+----------------------------------+
| a string                         |
+----------------------------------+

SELECT UNCOMPRESS('a string');
+------------------------+
| UNCOMPRESS('a string') |
+------------------------+
| NULL                   |
+------------------------+

UNCOMPRESSED_LENGTH

Syntax

UNCOMPRESSED_LENGTH(compressed_string)

Description

Returns the length that the compressed string had before being compressed with COMPRESS().

UNCOMPRESSED_LENGTH() returns NULL or an incorrect result if the string is not compressed.

Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits.

Examples

SELECT UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30)));
+-----------------------------------------------+
| UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30))) |
+-----------------------------------------------+
|                                            30 |
+-----------------------------------------------+

<<

Syntax

value1 << value2

Description

Converts a longlong (BIGINT) number (value1) to binary and shifts value2 units to the left.

Examples

SELECT 1 << 2;
+--------+
| 1 << 2 |
+--------+
|      4 |
+--------+

>>

Syntax

value1 >> value2

Description

Converts a longlong (BIGINT) number (value1) to binary and shifts value2 units to the right.

Examples

SELECT 4 >> 2;
+--------+
| 4 >> 2 |
+--------+
|      1 |
+--------+

BIT_COUNT

Syntax

BIT_COUNT(N)

Description

Returns the number of bits that are set in the argument N.

Examples

SELECT BIT_COUNT(29), BIT_COUNT(b'101010');
+---------------+----------------------+
| BIT_COUNT(29) | BIT_COUNT(b'101010') |
+---------------+----------------------+
|             4 |                    3 |
+---------------+----------------------+

^

Syntax

^

Description

Bitwise XOR. Converts the values to binary and compares bits. If one (and only one) of the corresponding bits is 1 is the resulting bit also 1.

Examples

SELECT 1 ^ 1;
+-------+
| 1 ^ 1 |
+-------+
|     0 |
+-------+

SELECT 1 ^ 0;
+-------+
| 1 ^ 0 |
+-------+
|     1 |
+-------+

SELECT 11 ^ 3;
+--------+
| 11 ^ 3 |
+--------+
|      8 |
+--------+

|

Syntax

|

Description

Bitwise OR. Converts the values to binary and compares bits. If either of the corresponding bits has a value of 1, the resulting bit is also 1.

See also bitwise AND.

Examples

SELECT 2|1;
+-----+
| 2|1 |
+-----+
|   3 |
+-----+

SELECT 29 | 15;
+---------+
| 29 | 15 |
+---------+
|      31 |
+---------+

GET_LOCK

Syntax

GET_LOCK(str,timeout)

Description

Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. Returns 1 if the lock was obtained successfully, 0 if the attempt timed out (for example, because another client has previously locked the name), or NULL if an error occurred (such as running out of memory or the thread was killed with mysqladmin kill).

A lock is released with RELEASE_LOCK(), when the connection terminates (either normally or abnormally), or before MariaDB 10.0.2, when the connection executes another GET_LOCK statement. From MariaDB 10.0.2, a connection can hold multiple locks at the same time, so a lock that is no longer needed needs to be explicitly released.

The IS_FREE_LOCK function returns whether a specified lock a free or not, and the IS_USED_LOCK whether the function is in use or not.

Locks obtained with GET_LOCK() do not interact with transactions. That is, committing a transaction does not release any such locks obtained during the transaction.

From MariaDB 10.0.2, it is also possible to recursively set the same lock. If a lock with the same name is set n times, it needs to be released n times as well.

str is case insensitive for GET_LOCK() and related functions. If str is an empty string or NULL, GET_LOCK() returns NULL and does nothing. From MariaDB 10.2.2, timeout supports microseconds. Before then, it was rounded to the closest integer.

If the metadata_lock_info plugin is installed, locks acquired with this function are visible in the Information Schema METADATA_LOCK_INFO table.

This function can be used to implement application locks or to simulate record locks. Names are locked on a server-wide basis. If a name has been locked by one client, GET_LOCK() blocks any request by another client for a lock with the same name. This allows clients that agree on a given lock name to use the name to perform cooperative advisory locking. But be aware that it also allows a client that is not among the set of cooperating clients to lock a name, either inadvertently or deliberately, and thus prevent any of the cooperating clients from locking that name. One way to reduce the likelihood of this is to use lock names that are database-specific or application-specific. For example, use lock names of the form db_name.str or app_name.str.

Statements using the GET_LOCK function are not safe for statement-based replication.

The patch to permit multiple locks was contributed by Konstantin "Kostja" Osipov (MDEV-3917).

Examples

SELECT GET_LOCK('lock1',10);
+----------------------+
| GET_LOCK('lock1',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT IS_FREE_LOCK('lock1'), IS_USED_LOCK('lock1');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_USED_LOCK('lock1') |
+-----------------------+-----------------------+
|                     0 |                    46 |
+-----------------------+-----------------------+

SELECT IS_FREE_LOCK('lock2'), IS_USED_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock2') | IS_USED_LOCK('lock2') |
+-----------------------+-----------------------+
|                     1 |                  NULL |
+-----------------------+-----------------------+

From MariaDB 10.0.2, multiple locks can be held:

SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') |
+-----------------------+-----------------------+
|                     0 |                     0 |
+-----------------------+-----------------------+

SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2');
+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') |
+-----------------------+-----------------------+
|                     1 |                     1 |
+-----------------------+-----------------------+

Before MariaDB 10.0.2, a connection could only hold a single lock:

SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') |
+-----------------------+-----------------------+
|                     1 |                     0 |
+-----------------------+-----------------------+

SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2');
+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') |
+-----------------------+-----------------------+
|                  NULL |                     1 |
+-----------------------+-----------------------+

From MariaDB 10.0.2, it is possible to hold the same lock recursively. This example is viewed using the metadata_lock_info plugin:

SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
Empty set (0.000 sec)

Timeout example: Connection 1:

SELECT GET_LOCK('lock4',10);
+----------------------+
| GET_LOCK('lock4',10) |
+----------------------+
|                    1 |
+----------------------+

Connection 2:

SELECT GET_LOCK('lock4',10);

After 10 seconds...

+----------------------+
| GET_LOCK('lock4',10) |
+----------------------+
|                    0 |
+----------------------+

Deadlocks are automatically detected and resolved. Connection 1:

SELECT GET_LOCK('lock5',10); 
+----------------------+
| GET_LOCK('lock5',10) |
+----------------------+
|                    1 |
+----------------------+

Connection 2:

SELECT GET_LOCK('lock6',10);
+----------------------+
| GET_LOCK('lock6',10) |
+----------------------+
|                    1 |
+----------------------+

Connection 1:

SELECT GET_LOCK('lock6',10); 
+----------------------+
| GET_LOCK('lock6',10) |
+----------------------+
|                    0 |
+----------------------+

Connection 2:

SELECT GET_LOCK('lock5',10);
ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction

See Also

INET6_ATON

Syntax

INET6_ATON(expr)

Description

Given an IPv6 or IPv4 network address as a string, returns a binary string that represents the numeric value of the address.

No trailing zone ID's or traling network masks are permitted. For IPv4 addresses, or IPv6 addresses with IPv4 address parts, no classful addresses or trailing port numbers are permitted and octal numbers are not supported.

The returned binary string will be VARBINARY(16) or VARBINARY(4) for IPv6 and IPv4 addresses respectively.

Returns NULL if the argument is not understood.

MariaDB starting with 10.5.0

From MariaDB 10.5.0, INET6_ATON can take INET6 as an argument.

Examples

SELECT HEX(INET6_ATON('10.0.1.1'));
+-----------------------------+
| HEX(INET6_ATON('10.0.1.1')) |
+-----------------------------+
| 0A000101                    |
+-----------------------------+

SELECT HEX(INET6_ATON('48f3::d432:1431:ba23:846f'));
+----------------------------------------------+
| HEX(INET6_ATON('48f3::d432:1431:ba23:846f')) |
+----------------------------------------------+
| 48F3000000000000D4321431BA23846F             |
+----------------------------------------------+

See Also

INET6_NTOA

Syntax

INET6_NTOA(expr)

Description

Given an IPv6 or IPv4 network address as a numeric binary string, returns the address as a nonbinary string in the connection character set.

The return string is lowercase, and is platform independent, since it does not use functions specific to the operating system. It has a maximum length of 39 characters.

Returns NULL if the argument is not understood.

Examples

SELECT INET6_NTOA(UNHEX('0A000101'));
+-------------------------------+
| INET6_NTOA(UNHEX('0A000101')) |
+-------------------------------+
| 10.0.1.1                      |
+-------------------------------+

SELECT INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F'));
+-------------------------------------------------------+
| INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F')) |
+-------------------------------------------------------+
| 48f3::d432:1431:ba23:846f                             |
+-------------------------------------------------------+

See Also

IS_IPV4

Syntax

IS_IPV4(expr)

Description

If the expression is a valid IPv4 address, returns 1, otherwise returns 0.

IS_IPV4() is stricter than INET_ATON(), but as strict as INET6_ATON(), in determining the validity of an IPv4 address. This implies that if IS_IPV4 returns 1, the same expression will always return a non-NULL result when passed to INET_ATON(), but that the reverse may not apply.

Examples

SELECT IS_IPV4('1110.0.1.1');
+-----------------------+
| IS_IPV4('1110.0.1.1') |
+-----------------------+
|                     0 |
+-----------------------+

SELECT IS_IPV4('48f3::d432:1431:ba23:846f');
+--------------------------------------+
| IS_IPV4('48f3::d432:1431:ba23:846f') |
+--------------------------------------+
|                                    0 |
+--------------------------------------+

IS_IPV4_COMPAT

Syntax

IS_IPV4_COMPAT(expr)

Description

Returns 1 if a given numeric binary string IPv6 address, such as returned by INET6_ATON(), is IPv4-compatible, otherwise returns 0.

MariaDB starting with 10.5.0

From MariaDB 10.5.0, when the argument is not INET6, automatic implicit CAST to INET6 is applied. As a consequence, IS_IPV4_COMPAT now understands arguments in both text representation and binary(16) representation. Before MariaDB 10.5.0, the function understood only binary(16) representation.

Examples

SELECT IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1'));
+------------------------------------------+
| IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1')) |
+------------------------------------------+
|                                        1 |
+------------------------------------------+

SELECT IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f'));
+-----------------------------------------------------------+
| IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f')) |
+-----------------------------------------------------------+
|                                                         0 |
+-----------------------------------------------------------+

IS_IPV4_MAPPED

Syntax

IS_IPV4_MAPPED(expr)

Description

Returns 1 if a given a numeric binary string IPv6 address, such as returned by INET6_ATON(), is a valid IPv4-mapped address, otherwise returns 0.

MariaDB starting with 10.5.0

From MariaDB 10.5.0, when the argument is not INET6, automatic implicit CAST to INET6 is applied. As a consequence, IS_IPV4_MAPPED now understands arguments in both text representation and binary(16) representation. Before MariaDB 10.5.0, the function understood only binary(16) representation.

Examples

SELECT IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1'));
+------------------------------------------+
| IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1')) |
+------------------------------------------+
|                                        0 |
+------------------------------------------+

SELECT IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1'));
+-----------------------------------------------+
| IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1')) |
+-----------------------------------------------+
|                                             1 |
+-----------------------------------------------+

~

Syntax

~

Description

Bitwise NOT. Converts the value to 4 bytes binary and inverts all bits.

Examples

SELECT 3 & ~1;
+--------+
| 3 & ~1 |
+--------+
|      2 |
+--------+

SELECT 5 & ~1;
+--------+
| 5 & ~1 |
+--------+
|      4 |
+--------+

TRUE FALSE

Description

The constants TRUE and FALSE evaluate to 1 and 0, respectively. The constant names can be written in any lettercase.

Examples

SELECT TRUE, true, FALSE, false;
+------+------+-------+-------+
| TRUE | TRUE | FALSE | FALSE |
+------+------+-------+-------+
|    1 |    1 |     0 |     0 |
+------+------+-------+-------+

BLOB and TEXT Data Types

Description

A BLOB is a binary large object that can hold a variable amount of data. The four BLOB types are

These differ only in the maximum length of the values they can hold.

The TEXT types are

These correspond to the four BLOB types and have the same maximum lengths and storage requirements.

MariaDB starting with 10.2.1

Starting from MariaDB 10.2.1, BLOB and TEXT columns can have a DEFAULT value.

MariaDB starting with 10.4.3

From MariaDB 10.4, it is possible to set a unique index on columns that use the BLOB or TEXT data types.

MASTER_GTID_WAIT

Syntax

MASTER_GTID_WAIT(gtid-list[, timeout)

Description

This function takes a string containing a comma-separated list of global transaction id's (similar to the value of, for example, gtid_binlog_pos). It waits until the value of gtid_slave_pos has the same or higher seq_no within all replication domains specified in the gtid-list; in other words, it waits until the slave has reached the specified GTID position.

An optional second argument gives a timeout in seconds. If the timeout expires before the specified GTID position is reached, then the function returns -1. Passing NULL or a negative number for the timeout means no timeout, and the function will wait indefinitely.

If the wait completes without a timeout, 0 is returned. Passing NULL for the gtid-list makes the function return NULL immediately, without waiting.

The gtid-list may be the empty string, in which case MASTER_GTID_WAIT() returns immediately. If the gtid-list contains fewer domains than gtid_slave_pos, then only those domains are waited upon. If gtid-list contains a domain that is not present in @@gtid_slave_pos, then MASTER_GTID_WAIT() will wait until an event containing such domain_id arrives on the slave (or until timed out or killed).

MASTER_GTID_WAIT() can be useful to ensure that a slave has caught up to a master. Simply take the value of gtid_binlog_pos on the master, and use it in a MASTER_GTID_WAIT() call on the slave; when the call completes, the slave will have caught up with that master position.

MASTER_GTID_WAIT() can also be used in client applications together with the last_gtid session variable. This is useful in a read-scaleout replication setup, where the application writes to a single master but divides the reads out to a number of slaves to distribute the load. In such a setup, there is a risk that an application could first do an update on the master, and then a bit later do a read on a slave, and if the slave is not fast enough, the data read from the slave might not include the update just made, possibly confusing the application and/or the end-user. One way to avoid this is to request the value of last_gtid on the master just after the update. Then before doing the read on the slave, do a MASTER_GTID_WAIT() on the value obtained from the master; this will ensure that the read is not performed until the slave has replicated sufficiently far for the update to have become visible.

Note that MASTER_GTID_WAIT() can be used even if the slave is configured not to use GTID for connections (CHANGE MASTER TO master_use_gtid=no). This is because from MariaDB 10, GTIDs are always logged on the master server, and always recorded on the slave servers.

Differences to MASTER_POS_WAIT()

  • MASTER_GTID_WAIT() is global; it waits for any master connection to reach the specified GTID position. MASTER_POS_WAIT() works only against a specific connection. This also means that while MASTER_POS_WAIT() aborts if its master connection is terminated with STOP SLAVE or due to an error, MASTER_GTID_WAIT() continues to wait while slaves are stopped.
  • MASTER_GTID_WAIT() can take its timeout as a floating-point value, so a timeout in fractional seconds is supported, eg. MASTER_GTID_WAIT("0-1-100", 0.5). (The minimum wait is one microsecond, 0.000001 seconds).
  • MASTER_GTID_WAIT() allows one to specify a timeout of zero in order to do a non-blocking check to see if the slaves have progressed to a specific GTID position (MASTER_POS_WAIT() takes a zero timeout as meaning an infinite wait). To do an infinite MASTER_GTID_WAIT(), specify a negative timeout, or omit the timeout argument.
  • MASTER_GTID_WAIT() does not return the number of events executed since the wait started, nor does it return NULL if a slave thread is stopped. It always returns either 0 for successful wait completed, or -1 for timeout reached (or NULL if the specified gtid-pos is NULL).

Since MASTER_GTID_WAIT() looks only at the seq_no part of the GTIDs, not the server_id, care is needed if a slave becomes diverged from another server so that two different GTIDs with the same seq_no (in the same domain) arrive at the same server. This situation is in any case best avoided; setting gtid_strict_mode is recommended, as this will prevent any such out-of-order sequence numbers from ever being replicated on a slave.

MASTER_POS_WAIT

Syntax

MASTER_POS_WAIT(log_name,log_pos[,timeout,["connection_name"]])

Description

This function is useful in replication for controlling primary/replica synchronization. It blocks until the replica has read and applied all updates up to the specified position (log_name,log_pos) in the primary log. The return value is the number of log events the replica had to wait for to advance to the specified position. The function returns NULL if the replica SQL thread is not started, the replica's primary information is not initialized, the arguments are incorrect, or an error occurs. It returns -1 if the timeout has been exceeded. If the replica SQL thread stops while MASTER_POS_WAIT() is waiting, the function returns NULL. If the replica is past the specified position, the function returns immediately.

If a timeout value is specified, MASTER_POS_WAIT() stops waiting when timeout seconds have elapsed. timeout must be greater than 0; a zero or negative timeout means no timeout.

The connection_name is used when you are using multi-source-replication. If you don't specify it, it's set to the value of the default_master_connection system variable.

Statements using the MASTER_POS_WAIT() function are not safe for replication.

CHAR BYTE

Description

The CHAR BYTE data type is an alias for the BINARY data type. This is a compatibility feature.

LONGBLOB

Syntax

LONGBLOB

Description

A BLOB column with a maximum length of 4,294,967,295 bytes or 4GB (232 - 1). The effective maximum length of LONGBLOB columns depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGBLOB value is stored using a four-byte length prefix that indicates the number of bytes in the value.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, BLOB is a synonym for LONGBLOB.

See Also

MEDIUMBLOB

Syntax

MEDIUMBLOB

Description

A BLOB column with a maximum length of 16,777,215 (224 - 1) bytes. Each MEDIUMBLOB value is stored using a three-byte length prefix that indicates the number of bytes in the value.

See Also

MEDIUMTEXT

Syntax

MEDIUMTEXT [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A TEXT column with a maximum length of 16,777,215 (224 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each MEDIUMTEXT value is stored using a three-byte length prefix that indicates the number of bytes in the value.

See Also

RELEASE_LOCK

Syntax

RELEASE_LOCK(str)

Description

Releases the lock named by the string str that was obtained with GET_LOCK(). Returns 1 if the lock was released, 0 if the lock was not established by this thread (in which case the lock is not released), and NULL if the named lock did not exist. The lock does not exist if it was never obtained by a call to GET_LOCK() or if it has previously been released.

str is case insensitive. If str is an empty string or NULL, RELEASE_LOCK() returns NULL and does nothing.

Statements using the RELEASE_LOCK() function are not safe for replication.

The DO statement is convenient to use with RELEASE_LOCK().

Examples

Connection1:

SELECT GET_LOCK('lock1',10);
+----------------------+
| GET_LOCK('lock1',10) |
+----------------------+
|                    1 |
+----------------------+

Connection 2:

SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
|                    1 |
+----------------------+

Connection 1:

SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'), RELEASE_LOCK('lock3');
+-----------------------+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') | RELEASE_LOCK('lock3') |
+-----------------------+-----------------------+-----------------------+
|                     1 |                     0 |                  NULL |
+-----------------------+-----------------------+-----------------------+

From MariaDB 10.0.2, it is possible to hold the same lock recursively. This example is viewed using the metadata_lock_info plugin:

SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
|                    1 |
+----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE           | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
|        46 | MDL_SHARED_NO_WRITE | NULL          | User lock | lock3        |            |
+-----------+---------------------+---------------+-----------+--------------+------------+

SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
Empty set (0.000 sec)

See Also

UUID

Syntax

UUID()

Description

Returns a Universally Unique Identifier (UUID).

A UUID is designed as a number that is globally unique in space and time. Two calls to UUID() are expected to generate two different values, even if these calls are performed on two separate computers that are not connected to each other.

UUID() results are intended to be unique, but cannot always be relied upon to unpredictable and unguessable, so should not be relied upon for these purposes.

A UUID is a 128-bit number represented by a utf8 string of five hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee format:

  • The first three numbers are generated from a timestamp.
  • The fourth number preserves temporal uniqueness in case the timestamp value loses monotonicity (for example, due to daylight saving time).
  • The fifth number is an IEEE 802 node number that provides spatial uniqueness. A random number is substituted if the latter is not available (for example, because the host computer has no Ethernet card, or we do not know how to find the hardware address of an interface on your operating system). In this case, spatial uniqueness cannot be guaranteed. Nevertheless, a collision should have very low probability.

Currently, the MAC address of an interface is taken into account only on FreeBSD and Linux. On other operating systems, MariaDB uses a randomly generated 48-bit number.

Statements using the UUID() function are not safe for replication.

The results are generated according to the "DCE 1.1:Remote Procedure Call" (Appendix A) CAE (Common Applications Environment) Specifications published by The Open Group in October 1997 (Document Number C706).

Examples

SELECT UUID();
+--------------------------------------+
| UUID()                               |
+--------------------------------------+
| cd41294a-afb0-11df-bc9b-00241dd75637 |
+--------------------------------------+

See Also

ROW

MariaDB starting with 10.3.0

The ROW data type was introduced in MariaDB 10.3.0.

Syntax

ROW (<field name> <data type> [{, <field name> <data type>}... ])

Description

ROW is a data type for stored procedure variables.

Features

ROW fields as normal variables

ROW fields (members) act as normal variables, and are able to appear in all query parts where a stored procedure variable is allowed:

  • Assignment is using the := operator and the SET command:
a.x:= 10;
a.x:= b.x;
SET a.x= 10, a.y=20, a.z= b.z;
  • Passing to functions and operators:
SELECT f1(rec.a), rec.a<10;
  • Clauses (select list, WHERE, HAVING, LIMIT, etc...,):
SELECT var.a, t1.b FROM t1 WHERE t1.b=var.b LIMIT var.c;
  • INSERT values:
INSERT INTO t1 VALUES (rec.a, rec.b, rec.c);
  • SELECT .. INTO targets
SELECT a,b INTO rec.a, rec.b FROM t1 WHERE t1.id=10;
EXECUTE IMMEDIATE 'CALL proc_with_out_param(?)' USING rec.a;

ROW type variables as FETCH targets

ROW type variables are allowed as FETCH targets:

FETCH cur INTO rec;

where cur is a CURSOR and rec is a ROW type stored procedure variable.

Note, currently an attempt to use FETCH for a ROW type variable returns this error:

ERROR 1328 (HY000): Incorrect number of FETCH variables

FETCH from a cursor cur into a ROW variable rec works as follows:

  • The number of fields in cur must match the number of fields in rec. Otherwise, an error is reported.
  • Assignment is done from left to right. The first cursor field is assigned to the first variable field, the second cursor field is assigned to the second variable field, etc.
  • Field names in rec are not important and can differ from field names in cur.

See FETCH Examples (below) for examples of using this with sql_mode=ORACLE and sql_mode=DEFAULT.

ROW type variables as SELECT...INTO targets

ROW type variables are allowed as SELECT..INTO targets with some differences depending on which sql_mode is in use.

  • When using sql_mode=ORACLE, table%ROWTYPE and cursor%ROWTYPE variables can be used as SELECT...INTO targets.
  • Using multiple ROW variables in the SELECT..INTO list will report an error.
  • Using ROW variables with a different column count than in the SELECT..INTO list will report an error.

See SELECT...INTO Examples (below) for examples of using this with sql_mode=ORACLE and sql_mode=DEFAULT.

Features not implemented

The following features are planned, but not implemented yet:

  • Returning a ROW type expression from a stored function (see MDEV-12252). This will need some grammar change to support field names after parentheses:
SELECT f1().x FROM DUAL;
  • Returning a ROW type expression from a built-in hybrid type function, such as CASE, IF, etc.
  • ROW of ROWs

Examples

Declaring a ROW in a stored procedure

DELIMITER $$
CREATE PROCEDURE p1()
BEGIN
  DECLARE r ROW (c1 INT, c2 VARCHAR(10));
  SET r.c1= 10;
  SET r.c2= 'test';
  INSERT INTO t1 VALUES (r.c1, r.c2);
END;
$$
DELIMITER ;
CALL p1();

FETCH Examples

A complete FETCH example for sql_mode=ORACLE:

DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
INSERT INTO t1 VALUES (20,'b20');
INSERT INTO t1 VALUES (30,'b30');

SET sql_mode=oracle;
DROP PROCEDURE IF EXISTS p1;
DELIMITER $$
CREATE PROCEDURE p1 AS
  rec ROW(a INT, b VARCHAR(32));
  CURSOR c IS SELECT a,b FROM t1;
BEGIN
  OPEN c;
  LOOP
    FETCH c INTO rec;
    EXIT WHEN c%NOTFOUND;
    SELECT ('rec=(' || rec.a ||','|| rec.b||')');
  END LOOP;
  CLOSE c;
END;
$$
DELIMITER ;
CALL p1();

A complete FETCH example for sql_mode=DEFAULT:

DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
INSERT INTO t1 VALUES (20,'b20');
INSERT INTO t1 VALUES (30,'b30');

SET sql_mode=DEFAULT;
DROP PROCEDURE IF EXISTS p1;
DELIMITER $$
CREATE PROCEDURE p1()
BEGIN
  DECLARE done INT DEFAULT FALSE;
  DECLARE rec ROW(a INT, b VARCHAR(32));
  DECLARE c CURSOR FOR SELECT a,b FROM t1;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
  OPEN c;
read_loop:
  LOOP
    FETCH c INTO rec;
    IF done THEN
      LEAVE read_loop;
    END IF;
    SELECT CONCAT('rec=(',rec.a,',',rec.b,')');
  END LOOP;
  CLOSE c;
END;
$$
DELIMITER ;
CALL p1();

SELECT...INTO Examples

A SELECT...INTO example for sql_mode=DEFAULT:

SET sql_mode=DEFAULT;
DROP TABLE IF EXISTS t1;
DROP PROCEDURE IF EXISTS p1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
DELIMITER $$
CREATE PROCEDURE p1()
BEGIN
  DECLARE rec1 ROW(a INT, b VARCHAR(32));
  SELECT * FROM t1 INTO rec1;
  SELECT rec1.a, rec1.b;
END;
$$
DELIMITER ;
CALL p1();

The above example returns:

+--------+--------+
| rec1.a | rec1.b |
+--------+--------+
|     10 | b10    |
+--------+--------+

A SELECT...INTO example for sql_mode=ORACLE:

SET sql_mode=ORACLE;
DROP TABLE IF EXISTS t1;
DROP PROCEDURE IF EXISTS p1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
DELIMITER $$
CREATE PROCEDURE p1 AS
  rec1 ROW(a INT, b VARCHAR(32));
BEGIN
  SELECT * FROM t1 INTO rec1;
  SELECT rec1.a, rec1.b;
END;
$$
DELIMITER ;
CALL p1();

The above example returns:

+--------+--------+
| rec1.a | rec1.b |
+--------+--------+
|     10 | b10    |
+--------+--------+

An example for sql_mode=ORACLE using table%ROWTYPE variables as SELECT..INTO targets:

SET sql_mode=ORACLE;
DROP TABLE IF EXISTS t1;
DROP PROCEDURE IF EXISTS p1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
DELIMITER $$
CREATE PROCEDURE p1 AS
  rec1 t1%ROWTYPE;
BEGIN
  SELECT * FROM t1 INTO rec1;
  SELECT rec1.a, rec1.b;
END;
$$
DELIMITER ;
CALL p1();

The above example returns:

+--------+--------+
| rec1.a | rec1.b |
+--------+--------+
|     10 | b10    |
+--------+--------+

An example for sql_mode=ORACLE using cursor%ROWTYPE variables as SELECT..INTO targets:

SET sql_mode=ORACLE;
DROP TABLE IF EXISTS t1;
DROP PROCEDURE IF EXISTS p1;
CREATE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b10');
DELIMITER $$
CREATE PROCEDURE p1 AS
  CURSOR cur1 IS SELECT * FROM t1;
  rec1 cur1%ROWTYPE;
BEGIN
  SELECT * FROM t1 INTO rec1;
  SELECT rec1.a, rec1.b;
END;
$$
DELIMITER ;
CALL p1();

The above example returns:

+--------+--------+
| rec1.a | rec1.b |
+--------+--------+
|     10 | b10    |
+--------+--------+

See Also

SET Data Type

Syntax

SET('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A set. A string object that can have zero or more values, each of which must be chosen from the list of values 'value1', 'value2', ... A SET column can have a maximum of 64 members. SET values are represented internally as integers.

SET values cannot contain commas.

If a SET contains duplicate values, an error will be returned if strict mode is enabled, or a warning if strict mode is not enabled.

See Also

TIMESTAMP

Syntax

TIMESTAMP [(<microsecond precision)]

Description

A timestamp in the format YYYY-MM-DD HH:MM:SS.ffffff.

The timestamp field is generally used to define at which moment in time a row was added or updated and by default will automatically be assigned the current datetime when a record is inserted or updated. The automatic properties only apply to the first TIMESTAMP in the record; subsequent TIMESTAMP columns will not be changed.

MariaDB starting with 10.1.2

MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store TIMESTAMPs using the same low-level format MySQL 5.6 uses.

For more information, see Internal Format.

Supported Values

MariaDB stores values that use the TIMESTAMP data type as the number of seconds since '1970-01-01 00:00:00' (UTC). This means that the TIMESTAMP data type can hold values between '1970-01-01 00:00:01' (UTC) and '2038-01-19 03:14:07' (UTC).

MariaDB can also store microseconds with a precision between 0 and 6. If no microsecond precision is specified, then 0 is used by default.

Automatic Values

MariaDB has special behavior for the first column that uses the TIMESTAMP data type in a specific table. For the first column that uses the TIMESTAMP data type in a specific table, MariaDB automatically assigns the following properties to the column:

  • DEFAULT CURRENT_TIMESTAMP
  • ON UPDATE CURRENT_TIMESTAMP

This means that if the column is not explicitly assigned a value in an INSERT or UPDATE query, then MariaDB will automatically initialize the column's value with the current date and time.

This automatic initialization for INSERT and UPDATE queries can also be explicitly enabled for a column that uses the TIMESTAMP data type by specifying the DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP clauses for the column. In these clauses, any synonym of CURRENT_TIMESTAMP is accepted, including CURRENT_TIMESTAMP(), NOW(), LOCALTIME, LOCALTIME(), LOCALTIMESTAMP, and LOCALTIMESTAMP().

This automatic initialization for INSERT queries can also be explicitly disabled for a column that uses the TIMESTAMP data type by specifying a constant DEFAULT value. For example, DEFAULT 0.

This automatic initialization for UPDATE queries can also be explicitly disabled for a column that uses the TIMESTAMP data type by specifying a DEFAULT clause for the column, but no ON UPDATE clause. If a DEFAULT clause is explicitly specified for a column that uses the TIMESTAMP data type, but an ON UPDATE clause is not specified for the column, then the timestamp value will not automatically change when an UPDATE statement is executed.

MariaDB also has special behavior if NULL is assigned to column that uses the TIMESTAMP data type. If the column is assigned the NULL value in an INSERT or UPDATE query, then MariaDB will automatically initialize the column's value with the current date and time. For details, see NULL values in MariaDB.

This automatic initialization for NULL values can also be explicitly disabled for a column that uses the TIMESTAMP data type by specifying the NULL attribute for the column. In this case, if the column's value is set to NULL, then the column's value will actually be set to NULL.

Time Zones

If a column uses the TIMESTAMP data type, then any inserted values are converted from the session's time zone to Coordinated Universal Time (UTC) when stored, and converted back to the session's time zone when retrieved.

MariaDB does not currently store any time zone identifier with the value of the TIMESTAMP data type. See MDEV-10018 for more information.

MariaDB does not currently support time zone literals that contain time zone identifiers. See MDEV-11829 for more information.

Limitations

  • Because the TIMESTAMP value is stored as Epoch Seconds, the timestamp value '1970-01-01 00:00:00' (UTC) is reserved since the second #0 is used to represent '0000-00-00 00:00:00'.
  • In MariaDB 5.5 and before there could only be one TIMESTAMP column per table that had CURRENT_TIMESTAMP defined as its default value. This limit has no longer applied since MariaDB 10.0.

SQL_MODE=MAXDB

If the SQL_MODE is set to MAXDB, TIMESTAMP fields will be silently converted to DATETIME.

Internal Format

In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable.

Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format.

In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225).

For instance, if you have a TIMESTAMP column in your table:

SHOW VARIABLES LIKE 'mysql56_temporal_format';

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON    |
+-------------------------+-------+

ALTER TABLE example_table MODIFY ts_col TIMESTAMP;

When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one.

In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format.

Starting from MariaDB 10.5.1 columns with old temporal formats are marked with a /* mariadb-5.3 */ comment in the output of SHOW CREATE TABLE, SHOW COLUMNS, DESCRIBE statements, as well as in the COLUMN_TYPE column of the INFORMATION_SCHEMA.COLUMNS Table.

SHOW CREATE TABLE mariadb5312_timestamp\G
*************************** 1. row ***************************
       Table: mariadb5312_timestamp
Create Table: CREATE TABLE `mariadb5312_timestamp` (
  `ts0` timestamp /* mariadb-5.3 */ NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(),
  `ts6` timestamp(6) /* mariadb-5.3 */ NOT NULL DEFAULT '0000-00-00 00:00:00.000000'
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Note: Prior to MySQL 4.1 a different format for the TIMESTAMP datatype was used. This format is unsupported in MariaDB 5.1 and upwards.

Examples

CREATE TABLE t (id INT, ts TIMESTAMP);

DESC t;
+-------+-----------+------+-----+-------------------+-----------------------------+
| Field | Type      | Null | Key | Default           | Extra                       |
+-------+-----------+------+-----+-------------------+-----------------------------+
| id    | int(11)   | YES  |     | NULL              |                             |
| ts    | timestamp | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
+-------+-----------+------+-----+-------------------+-----------------------------+

INSERT INTO t(id)  VALUES (1),(2);

SELECT * FROM t;
+------+---------------------+
| id   | ts                  |
+------+---------------------+
|    1 | 2013-07-22 12:50:05 |
|    2 | 2013-07-22 12:50:05 |
+------+---------------------+

INSERT INTO t  VALUES (3,NULL),(4,'2001-07-22 12:12:12');

SELECT * FROM t;
+------+---------------------+
| id   | ts                  |
+------+---------------------+
|    1 | 2013-07-22 12:50:05 |
|    2 | 2013-07-22 12:50:05 |
|    3 | 2013-07-22 12:51:56 |
|    4 | 2001-07-22 12:12:12 |
+------+---------------------+

Converting to Unix epoch:

SELECT ts, UNIX_TIMESTAMP(ts) FROM t;
+---------------------+--------------------+
| ts                  | UNIX_TIMESTAMP(ts) |
+---------------------+--------------------+
| 2013-07-22 12:50:05 |         1374490205 |
| 2013-07-22 12:50:05 |         1374490205 |
| 2013-07-22 12:51:56 |         1374490316 |
| 2001-07-22 12:12:12 |          995796732 |
+---------------------+--------------------+

Update also changes the timestamp:

UPDATE t set id=5 WHERE id=1;

SELECT * FROM t;
+------+---------------------+
| id   | ts                  |
+------+---------------------+
|    5 | 2013-07-22 14:52:33 |
|    2 | 2013-07-22 12:50:05 |
|    3 | 2013-07-22 12:51:56 |
|    4 | 2001-07-22 12:12:12 |
+------+---------------------+

Default NULL:

CREATE TABLE t2 (id INT, ts TIMESTAMP NULL ON UPDATE CURRENT_TIMESTAMP);

INSERT INTO t(id)  VALUES (1),(2);

SELECT * FROM t2;

INSERT INTO t2(id)  VALUES (1),(2);

SELECT * FROM t2;
+------+------+
| id   | ts   |
+------+------+
|    1 | NULL |
|    2 | NULL |
+------+------+

UPDATE t2 SET id=3 WHERE id=1;

SELECT * FROM t2;
+------+---------------------+
| id   | ts                  |
+------+---------------------+
|    3 | 2013-07-22 15:32:22 |
|    2 | NULL                |
+------+---------------------+

Only the first timestamp is automatically inserted and updated:

CREATE TABLE t3 (id INT, ts1 TIMESTAMP, ts2 TIMESTAMP);

INSERT INTO t3(id)  VALUES (1),(2);

SELECT * FROM t3;
+------+---------------------+---------------------+
| id   | ts1                 | ts2                 |
+------+---------------------+---------------------+
|    1 | 2013-07-22 15:35:07 | 0000-00-00 00:00:00 |
|    2 | 2013-07-22 15:35:07 | 0000-00-00 00:00:00 |
+------+---------------------+---------------------+

DESC t3;
+-------+-----------+------+-----+---------------------+-----------------------------+
| Field | Type      | Null | Key | Default             | Extra                       |
+-------+-----------+------+-----+---------------------+-----------------------------+
| id    | int(11)   | YES  |     | NULL                |                             |
| ts1   | timestamp | NO   |     | CURRENT_TIMESTAMP   | on update CURRENT_TIMESTAMP |
| ts2   | timestamp | NO   |     | 0000-00-00 00:00:00 |                             |
+-------+-----------+------+-----+---------------------+-----------------------------+

Explicitly setting a timestamp with the CURRENT_TIMESTAMP function:

INSERT INTO t3(id,ts2)  VALUES (3,CURRENT_TIMESTAMP());

SELECT * FROM t3;
+------+---------------------+---------------------+
| id   | ts1                 | ts2                 |
+------+---------------------+---------------------+
|    1 | 2013-07-22 15:35:07 | 0000-00-00 00:00:00 |
|    2 | 2013-07-22 15:35:07 | 0000-00-00 00:00:00 |
|    3 | 2013-07-22 15:38:52 | 2013-07-22 15:38:52 |
+------+---------------------+---------------------+

Specifying the timestamp as NOT NULL:

CREATE TABLE t4 (id INT, ts TIMESTAMP NOT NULL);

INSERT INTO t4(id)  VALUES (1);
SELECT SLEEP(1);
INSERT INTO t4(id,ts) VALUES (2,NULL);

SELECT * FROM t4;

See Also

TINYBLOB

Syntax

TINYBLOB

Description

A BLOB column with a maximum length of 255 (28 - 1) bytes. Each TINYBLOB value is stored using a one-byte length prefix that indicates the number of bytes in the value.

See Also

TINYTEXT

Syntax

TINYTEXT [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A TEXT column with a maximum length of 255 (28 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each TINYTEXT value is stored using a one-byte length prefix that indicates the number of bytes in the value.

See Also

VALUES / VALUE

Syntax

MariaDB starting with 10.3.3
VALUE(col_name) 
MariaDB until 10.3.2
VALUES(col_name) 

Description

In an INSERT ... ON DUPLICATE KEY UPDATE statement, you can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the statement. In other words, VALUES(col_name) in the UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts.

The VALUES() function is meaningful only in INSERT ... ON DUPLICATE KEY UPDATE statements and returns NULL otherwise.

In MariaDB 10.3.3 this function was renamed to VALUE(), because it's incompatible with the standard Table Value Constructors syntax, implemented in MariaDB 10.3.3.

The VALUES() function can still be used even from MariaDB 10.3.3, but only in INSERT ... ON DUPLICATE KEY UPDATE statements; it's a syntax error otherwise.

Examples

MariaDB starting with 10.3.3
INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6)
    ON DUPLICATE KEY UPDATE c=VALUE(a)+VALUE(b);
MariaDB until 10.3.2
INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6)
    ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

||

Syntax

OR, ||

Description

Logical OR. When both operands are non-NULL, the result is 1 if any operand is non-zero, and 0 otherwise. With a NULL operand, the result is 1 if the other operand is non-zero, and NULL otherwise. If both operands are NULL, the result is NULL.

For this operator, short-circuit evaluation can be used.

Note that, if the PIPES_AS_CONCAT SQL_MODE is set, || is used as a string concatenation operator. This means that a || b is the same as CONCAT(a,b). See CONCAT() for details.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, || ignores NULL.

Examples

SELECT 1 || 1;
+--------+
| 1 || 1 |
+--------+
|      1 |
+--------+

SELECT 1 || 0;
+--------+
| 1 || 0 |
+--------+
|      1 |
+--------+

SELECT 0 || 0;
+--------+
| 0 || 0 |
+--------+
|      0 |
+--------+

SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
|      NULL |
+-----------+

SELECT 1 || NULL;
+-----------+
| 1 || NULL |
+-----------+
|         1 |
+-----------+

In Oracle mode, from MariaDB 10.3:

SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
| 0         |
+-----------+

See Also

XOR

Syntax

XOR

Description

XOR stands for eXclusive OR. Returns NULL if either operand is NULL. For non-NULL operands, evaluates to 1 if an odd number of operands is non-zero, otherwise 0 is returned.

Examples

SELECT 1 XOR 1;
+---------+
| 1 XOR 1 |
+---------+
|       0 |
+---------+

SELECT 1 XOR 0;
+---------+
| 1 XOR 0 |
+---------+
|       1 |
+---------+

SELECT 1 XOR NULL;
+------------+
| 1 XOR NULL |
+------------+
|       NULL |
+------------+

In the following example, the right 1 XOR 1 is evaluated first, and returns 0. Then, 1 XOR 0 is evaluated, and 1 is returned.

SELECT 1 XOR 1 XOR 1;
+---------------+
| 1 XOR 1 XOR 1 |
+---------------+
|             1 |
+---------------+

Assignment Operator (=)

Syntax

identifier = expr

Description

The equal sign is used as both an assignment operator in certain contexts, and as a comparison operator. When used as assignment operator, the value on the right is assigned to the variable (or column, in some contexts) on the left.

Since its use can be ambiguous, unlike the := assignment operator, the = assignment operator cannot be used in all contexts, and is only valid as part of a SET statement, or the SET clause of an UPDATE statement

This operator works with both user-defined variables and local variables.

Examples

UPDATE table_name SET x = 2 WHERE x > 100;
SET @x = 1, @y := 2;

Stored Aggregate Functions

MariaDB starting with 10.3.3

The ability to create stored aggregate functions was added in MariaDB 10.3.3.

Aggregate functions are functions that are computed over a sequence of rows and return one result for the sequence of rows.

Creating a custom aggregate function is done using the CREATE FUNCTION statement with two main differences:

  • The addition of the AGGREGATE keyword, so CREATE AGGREGATE FUNCTION
  • The FETCH GROUP NEXT ROW instruction inside the loop
  • Oracle PL/SQL compatibility using SQL/PL is provided

Standard Syntax

CREATE AGGREGATE FUNCTION function_name (parameters) RETURNS return_type
BEGIN
      All types of declarations
      DECLARE CONTINUE HANDLER FOR NOT FOUND RETURN return_val;
      LOOP
           FETCH GROUP NEXT ROW; // fetches next row from table
           other instructions
      END LOOP;
END

Stored aggregate functions were a 2016 Google Summer of Code project by Varun Gupta.

Using SQL/PL

SET sql_mode=Oracle;
DELIMITER //

CREATE AGGREGATE FUNCTION function_name (parameters) RETURN return_type
   declarations
BEGIN
   LOOP
      FETCH GROUP NEXT ROW; -- fetches next row from table
      -- other instructions

   END LOOP;
EXCEPTION
   WHEN NO_DATA_FOUND THEN
      RETURN return_val;
END //

DELIMITER ;

Examples

First a simplified example:

CREATE TABLE marks(stud_id INT, grade_count INT);

INSERT INTO marks VALUES (1,6), (2,4), (3,7), (4,5), (5,8);

SELECT * FROM marks;
+---------+-------------+
| stud_id | grade_count |
+---------+-------------+
|       1 |           6 |
|       2 |           4 |
|       3 |           7 |
|       4 |           5 |
|       5 |           8 |
+---------+-------------+

DELIMITER //
CREATE AGGREGATE FUNCTION IF NOT EXISTS aggregate_count(x INT) RETURNS INT
BEGIN
 DECLARE count_students INT DEFAULT 0;
 DECLARE CONTINUE HANDLER FOR NOT FOUND
 RETURN count_students;
      LOOP
          FETCH GROUP NEXT ROW;
          IF x  THEN
            SET count_students = count_students+1;
          END IF;
      END LOOP;
END //
DELIMITER ;

A non-trivial example that cannot easily be rewritten using existing functions:

DELIMITER //
CREATE AGGREGATE FUNCTION medi_int(x INT) RETURNS DOUBLE
BEGIN
  DECLARE CONTINUE HANDLER FOR NOT FOUND
    BEGIN
      DECLARE res DOUBLE;
      DECLARE cnt INT DEFAULT (SELECT COUNT(*) FROM tt);
      DECLARE lim INT DEFAULT (cnt-1) DIV 2;
      IF cnt % 2 = 0 THEN
        SET res = (SELECT AVG(a) FROM (SELECT a FROM tt ORDER BY a LIMIT lim,2) ttt);
      ELSE
        SET res = (SELECT a FROM tt ORDER BY a LIMIT lim,1);
      END IF;
      DROP TEMPORARY TABLE tt;
      RETURN res;
    END;
  CREATE TEMPORARY TABLE tt (a INT);
  LOOP
    FETCH GROUP NEXT ROW;
    INSERT INTO tt VALUES (x);
  END LOOP;
END //
DELIMITER ;

SQL/PL Example

This uses the same marks table as created above.

SET sql_mode=Oracle;
DELIMITER //

CREATE AGGREGATE FUNCTION aggregate_count(x INT) RETURN INT AS count_students INT DEFAULT 0;
BEGIN
   LOOP
      FETCH GROUP NEXT ROW;
      IF x  THEN
        SET count_students := count_students+1;
      END IF;
   END LOOP;
EXCEPTION
   WHEN NO_DATA_FOUND THEN
      RETURN count_students;
END aggregate_count //
DELIMITER ;

SELECT aggregate_count(stud_id) FROM marks;

See Also

AVG

Syntax

AVG([DISTINCT] expr)

Description

Returns the average value of expr. The DISTINCT option can be used to return the average of the distinct values of expr. NULL values are ignored. It is an aggregate function, and so can be used with the GROUP BY clause.

AVG() returns NULL if there were no matching rows.

From MariaDB 10.2.0, AVG() can be used as a window function.

Examples

CREATE TABLE sales (sales_value INT);

INSERT INTO sales VALUES(10),(20),(20),(40);

SELECT AVG(sales_value) FROM sales;
+------------------+
| AVG(sales_value) |
+------------------+
|          22.5000 |
+------------------+

SELECT AVG(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| AVG(DISTINCT(sales_value)) |
+----------------------------+
|                    23.3333 |
+----------------------------+

Commonly, AVG() is used with a GROUP BY clause:

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, AVG(score) FROM student GROUP BY name;
+---------+------------+
| name    | AVG(score) |
+---------+------------+
| Chun    |    74.0000 |
| Esben   |    37.0000 |
| Kaolin  |    72.0000 |
| Tatiana |    85.0000 |
+---------+------------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data:

SELECT name,test,AVG(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL  |         31 |
+------+------+------------+

As a window function:

CREATE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, test, score, AVG(score) OVER (PARTITION BY test) 
    AS average_by_test FROM student_test;
+---------+--------+-------+-----------------+
| name    | test   | score | average_by_test |
+---------+--------+-------+-----------------+
| Chun    | SQL    |    75 |         65.2500 |
| Chun    | Tuning |    73 |         68.7500 |
| Esben   | SQL    |    43 |         65.2500 |
| Esben   | Tuning |    31 |         68.7500 |
| Kaolin  | SQL    |    56 |         65.2500 |
| Kaolin  | Tuning |    88 |         68.7500 |
| Tatiana | SQL    |    87 |         65.2500 |
| Tatiana | Tuning |    83 |         68.7500 |
+---------+--------+-------+-----------------+

See Also

BIT_AND

Syntax

BIT_AND(expr) [over_clause]

Description

Returns the bitwise AND of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_AND will return a value with all bits set to 1. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_AND can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_AND(NULL);
+----------------------+
| BIT_AND(NULL)        |
+----------------------+
| 18446744073709551615 |
+----------------------+

See Also

BIT_OR

Syntax

BIT_OR(expr) [over_clause]

Description

Returns the bitwise OR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_OR will return a value with all bits set to 0. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_OR can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_OR(NULL);
+--------------+
| BIT_OR(NULL) |
+--------------+
|            0 |
+--------------+

See Also

CLOSE

Syntax

CLOSE cursor_name

Description

This statement closes a previously opened cursor. The cursor must have been previously opened or else an error occurs.

If not closed explicitly, a cursor is closed at the end of the compound statement in which it was declared.

See Cursor Overview for an example.

See Also

DECLARE CURSOR

Syntax

<= MariaDB 10.2

DECLARE cursor_name CURSOR FOR select_statement

From MariaDB 10.3

DECLARE cursor_name CURSOR [(cursor_formal_parameter[,...])] FOR select_statement

cursor_formal_parameter:
    name type [collate clause]

From MariaDB 10.8

DECLARE cursor_name CURSOR [(cursor_formal_parameter[,...])] FOR select_statement

cursor_formal_parameter:
    [IN] name type [collate clause]

Description

This statement declares a cursor. Multiple cursors may be declared in a stored program, but each cursor in a given block must have a unique name.

select_statement is not executed until the OPEN statement is executed. It is important to remember this if the query produces an error, or calls functions which have side effects.

A SELECT associated to a cursor can use variables, but the query itself cannot be a variable, and cannot be dynamically composed. The SELECT statement cannot have an INTO clause.

Cursors must be declared before HANDLERs, but after local variables and CONDITIONs.

Parameters

MariaDB starting with 10.3.0

From MariaDB 10.3.0, cursors can have parameters. This is a non-standard SQL extension. Cursor parameters can appear in any part of the DECLARE CURSOR select_statement where a stored procedure variable is allowed (select list, WHERE, HAVING, LIMIT etc).

IN

MariaDB starting with 10.8.0

From MariaDB 10.8.0 preview release, the IN qualifier is supported in the cursor_format_parameter part of the syntax.

See Cursor Overview for an example.

See Also

FETCH

Syntax

FETCH cursor_name INTO var_name [, var_name] ...

Description

This statement fetches the next row (if a row exists) using the specified open cursor, and advances the cursor pointer.

var_name can be a local variable, but not a user-defined variable.

If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition).

See Cursor Overview for an example.

See Also

GOTO

MariaDB starting with 10.3

The GOTO statement was introduced in MariaDB 10.3 for Oracle compatibility.

Syntax

GOTO label

Description

The GOTO statement causes the code to jump to the specified label, and continue operating from there. It is only accepted when in Oracle mode.

Example

SET sql_mode=ORACLE;

DELIMITER //

CREATE OR REPLACE PROCEDURE p1 AS

BEGIN

  SELECT 1;
  GOTO label;
  SELECT 2;
  <<label>>
  SELECT 3;

END;

//

DELIMITER 

call p1();
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.000 sec)

+---+
| 3 |
+---+
| 3 |
+---+
1 row in set (0.000 sec)

IF

Syntax

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF;

Description

IF implements a basic conditional construct. If the search_condition evaluates to true, the corresponding SQL statement list is executed. If no search_condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

See Also

BIT_XOR

Syntax

BIT_XOR(expr) [over_clause]

Description

Returns the bitwise XOR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_XOR will return a value with all bits set to 0. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_XOR can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_XOR(NULL);
+---------------+
| BIT_XOR(NULL) |
+---------------+
|             0 |
+---------------+

See Also

COUNT

Syntax

COUNT(expr)

Description

Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value. It is an aggregate function, and so can be used with the GROUP BY clause.

COUNT(*) counts the total number of rows in a table.

COUNT() returns 0 if there were no matching rows.

From MariaDB 10.2.0, COUNT() can be used as a window function.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT COUNT(*) FROM student;
+----------+
| COUNT(*) |
+----------+
|        8 |
+----------+

COUNT(DISTINCT) example:

SELECT COUNT(DISTINCT (name)) FROM student;
+------------------------+
| COUNT(DISTINCT (name)) |
+------------------------+
|                      4 |
+------------------------+

As a window function

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, COUNT(score) OVER (PARTITION BY name) 
    AS tests_written FROM student_test;
+---------+--------+-------+---------------+
| name    | test   | score | tests_written |
+---------+--------+-------+---------------+
| Chun    | SQL    |    75 |             2 |
| Chun    | Tuning |    73 |             2 |
| Esben   | SQL    |    43 |             2 |
| Esben   | Tuning |    31 |             2 |
| Kaolin  | SQL    |    56 |             2 |
| Kaolin  | Tuning |    88 |             2 |
| Tatiana | SQL    |    87 |             1 |
+---------+--------+-------+---------------+

See Also

MAX

Syntax

MAX([DISTINCT] expr)

Description

Returns the largest, or maximum, value of expr. MAX() can also take a string argument in which case it returns the maximum string value. The DISTINCT keyword can be used to find the maximum of the distinct values of expr, however, this produces the same result as omitting DISTINCT.

Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MAX() may produce a different highest result than ORDER BY DESC.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, MAX() can be used as a window function.

MAX() returns NULL if there were no matching rows.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, MAX(score) FROM student GROUP BY name;
+---------+------------+
| name    | MAX(score) |
+---------+------------+
| Chun    |         75 |
| Esben   |         43 |
| Kaolin  |         88 |
| Tatiana |         87 |
+---------+------------+

MAX string:

SELECT MAX(name) FROM student;
+-----------+
| MAX(name) |
+-----------+
| Tatiana   |
+-----------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data:

SELECT name,test,MAX(SCORE) FROM student;
+------+------+------------+
| name | test | MAX(SCORE) |
+------+------+------------+
| Chun | SQL  |         88 |
+------+------+------------+

Difference between ORDER BY DESC and MAX():

CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a'));

INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a');

SELECT MAX(grade) FROM student2;
+------------+
| MAX(grade) |
+------------+
| c          |
+------------+

SELECT grade FROM student2 ORDER BY grade DESC LIMIT 1;
+-------+
| grade |
+-------+
| a     |
+-------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, MAX(score) 
  OVER (PARTITION BY name) AS highest_score FROM student_test;
+---------+--------+-------+---------------+
| name    | test   | score | highest_score |
+---------+--------+-------+---------------+
| Chun    | SQL    |    75 |            75 |
| Chun    | Tuning |    73 |            75 |
| Esben   | SQL    |    43 |            43 |
| Esben   | Tuning |    31 |            43 |
| Kaolin  | SQL    |    56 |            88 |
| Kaolin  | Tuning |    88 |            88 |
| Tatiana | SQL    |    87 |            87 |
+---------+--------+-------+---------------+

See Also

ITERATE

Syntax

ITERATE label

ITERATE can appear only within LOOP, REPEAT, and WHILE statements. ITERATE means "do the loop again", and uses the statement's label to determine which statements to repeat. The label must be in the same stored program, not in a caller procedure.

If you try to use ITERATE with a non-existing label, or if the label is associated to a construct which is not a loop, the following error will be produced:

ERROR 1308 (42000): ITERATE with no matching label: <label_name>

Below is an example of how ITERATE might be used:

CREATE PROCEDURE doiterate(p1 INT)
BEGIN
  label1: LOOP
    SET p1 = p1 + 1;
    IF p1 < 10 THEN ITERATE label1; END IF;
    LEAVE label1;
  END LOOP label1;
  SET @x = p1;
END

See Also

  • LEAVE - Exits a loop (or any labeled code block)

LOOP

Syntax

[begin_label:] LOOP
    statement_list
END LOOP [end_label]

Description

LOOP implements a simple loop construct, enabling repeated execution of the statement list, which consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. The statements within the loop are repeated until the loop is exited; usually this is accomplished with a LEAVE statement.

A LOOP statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

See Delimiters in the mysql client for more on delimiter usage in the client.

See Also

MIN

Syntax

MIN([DISTINCT] expr)

Description

Returns the minimum value of expr. MIN() may take a string argument, in which case it returns the minimum string value. The DISTINCT keyword can be used to find the minimum of the distinct values of expr, however, this produces the same result as omitting DISTINCT.

Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MIN() may produce a different lowest result than ORDER BY ASC.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, MIN() can be used as a window function.

MIN() returns NULL if there were no matching rows.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, MIN(score) FROM student GROUP BY name;
+---------+------------+
| name    | MIN(score) |
+---------+------------+
| Chun    |         73 |
| Esben   |         31 |
| Kaolin  |         56 |
| Tatiana |         83 |
+---------+------------+

MIN() with a string:

SELECT MIN(name) FROM student;
+-----------+
| MIN(name) |
+-----------+
| Chun      |
+-----------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data:

SELECT name,test,MIN(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL  |         31 |
+------+------+------------+

Difference between ORDER BY ASC and MIN():

CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a'));

INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a');

SELECT MIN(grade) FROM student2;
+------------+
| MIN(grade) |
+------------+
| a          |
+------------+

SELECT grade FROM student2 ORDER BY grade ASC LIMIT 1;
+-------+
| grade |
+-------+
| b     |
+-------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);


SELECT name, test, score, MIN(score) 
  OVER (PARTITION BY name) AS lowest_score FROM student_test;
+---------+--------+-------+--------------+
| name    | test   | score | lowest_score |
+---------+--------+-------+--------------+
| Chun    | SQL    |    75 |           73 |
| Chun    | Tuning |    73 |           73 |
| Esben   | SQL    |    43 |           31 |
| Esben   | Tuning |    31 |           31 |
| Kaolin  | SQL    |    56 |           56 |
| Kaolin  | Tuning |    88 |           56 |
| Tatiana | SQL    |    87 |           87 |
+---------+--------+-------+--------------+

See Also

STD

Syntax

STD(expr)

Description

Returns the population standard deviation of expr. This is an extension to standard SQL. The standard SQL function STDDEV_POP() can be used instead.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STD() can be used as a window function.

This function returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

STDDEV

Syntax

STDDEV(expr)

Description

Returns the population standard deviation of expr. This function is provided for compatibility with Oracle. The standard SQL function STDDEV_POP() can be used instead.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV() can be used as a window function.

This function returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

OPEN

Syntax

<= MariaDB 10.2

OPEN cursor_name

From MariaDB 10.3

OPEN cursor_name [expression[,...]];

Description

This statement opens a cursor which was previously declared with DECLARE CURSOR.

The query associated to the DECLARE CURSOR is executed when OPEN is executed. It is important to remember this if the query produces an error, or calls functions which have side effects.

This is necessary in order to FETCH rows from a cursor.

See Cursor Overview for an example.

See Also

RETURN

Syntax

RETURN expr 

The RETURN statement terminates execution of a stored function and returns the value expr to the function caller. There must be at least one RETURN statement in a stored function. If the function has multiple exit points, all exit points must have a RETURN.

This statement is not used in stored procedures, triggers, or events. LEAVE can be used instead.

The following example shows that RETURN can return the result of a scalar subquery:

CREATE FUNCTION users_count() RETURNS BOOL
   READS SQL DATA
BEGIN
   RETURN (SELECT COUNT(DISTINCT User) FROM mysql.user);
END;

STDDEV_POP

Syntax

STDDEV_POP(expr)

Description

Returns the population standard deviation of expr (the square root of VAR_POP()). You can also use STD() or STDDEV(), which are equivalent but not standard SQL.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV_POP() can be used as a window function.

STDDEV_POP() returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

  • STD (equivalent, non-standard SQL)
  • STDDEV (equivalent, Oracle-compatible non-standard SQL)
  • VAR_POP (variance)
  • STDDEV_SAMP (sample standard deviation)

SUM

Syntax

SUM([DISTINCT] expr)

Description

Returns the sum of expr. If the return set has no rows, SUM() returns NULL. The DISTINCT keyword can be used to sum only the distinct values of expr.

From MariaDB 10.2.0, SUM() can be used as a window function, although not with the DISTINCT specifier.

Examples

CREATE TABLE sales (sales_value INT);
INSERT INTO sales VALUES(10),(20),(20),(40);

SELECT SUM(sales_value) FROM sales;
+------------------+
| SUM(sales_value) |
+------------------+
|               90 |
+------------------+

SELECT SUM(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| SUM(DISTINCT(sales_value)) |
+----------------------------+
|                         70 |
+----------------------------+

Commonly, SUM is used with a GROUP BY clause:

CREATE TABLE sales (name CHAR(10), month CHAR(10), units INT);

INSERT INTO sales VALUES 
  ('Chun', 'Jan', 75), ('Chun', 'Feb', 73),
  ('Esben', 'Jan', 43), ('Esben', 'Feb', 31),
  ('Kaolin', 'Jan', 56), ('Kaolin', 'Feb', 88),
  ('Tatiana', 'Jan', 87), ('Tatiana', 'Feb', 83);

SELECT name, SUM(units) FROM sales GROUP BY name;
+---------+------------+
| name    | SUM(units) |
+---------+------------+
| Chun    |        148 |
| Esben   |         74 |
| Kaolin  |        144 |
| Tatiana |        170 |
+---------+------------+

The GROUP BY clause is required when using an aggregate function along with regular column data, otherwise the result will be a mismatch, as in the following common type of mistake:

SELECT name,SUM(units) FROM sales
;+------+------------+
| name | SUM(units) |
+------+------------+
| Chun |        536 |
+------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, SUM(score) OVER (PARTITION BY name) AS total_score FROM student_test;
+---------+--------+-------+-------------+
| name    | test   | score | total_score |
+---------+--------+-------+-------------+
| Chun    | SQL    |    75 |         148 |
| Chun    | Tuning |    73 |         148 |
| Esben   | SQL    |    43 |          74 |
| Esben   | Tuning |    31 |          74 |
| Kaolin  | SQL    |    56 |         144 |
| Kaolin  | Tuning |    88 |         144 |
| Tatiana | SQL    |    87 |          87 |
+---------+--------+-------+-------------+

See Also

VARIANCE

Syntax

VARIANCE(expr) 

Description

Returns the population standard variance of expr. This is an extension to standard SQL. The standard SQL function VAR_POP() can be used instead.

Variance is calculated by

  • working out the mean for the set
  • for each number, subtracting the mean and squaring the result
  • calculate the average of the resulting differences

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VARIANCE() can be used as a window function.

VARIANCE() returns NULL if there were no matching rows.

Examples

CREATE TABLE v(i tinyint);

INSERT INTO v VALUES(101),(99);

SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
|      1.0000 |
+-------------+

INSERT INTO v VALUES(120),(80);

SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
|    200.5000 |
+-------------+

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_POP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         287.1875 |
| Chun    | Tuning |    73 |         582.0000 |
| Esben   | SQL    |    43 |         287.1875 |
| Esben   | Tuning |    31 |         582.0000 |
| Kaolin  | SQL    |    56 |         287.1875 |
| Kaolin  | Tuning |    88 |         582.0000 |
| Tatiana | SQL    |    87 |         287.1875 |
+---------+--------+-------+------------------+

See Also

WHILE

Syntax

[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]

Description

The statement list within a WHILE statement is repeated as long as the search_condition is true. statement_list consists of one or more statements. If the loop must be executed at least once, REPEAT ... LOOP can be used instead.

A WHILE statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

Examples

CREATE PROCEDURE dowhile()
BEGIN
  DECLARE v1 INT DEFAULT 5;

  WHILE v1 > 0 DO
    ...
    SET v1 = v1 - 1;
  END WHILE;
END

VAR_POP

Syntax

VAR_POP(expr)

Description

Returns the population standard variance of expr. It considers rows as the whole population, not as a sample, so it has the number of rows as the denominator. You can also use VARIANCE(), which is equivalent but is not standard SQL.

Variance is calculated by

  • working out the mean for the set
  • for each number, subtracting the mean and squaring the result
  • calculate the average of the resulting differences

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VAR_POP() can be used as a window function.

VAR_POP() returns NULL if there were no matching rows.

Examples

CREATE TABLE v(i tinyint);

INSERT INTO v VALUES(101),(99);

SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
|     1.0000 |
+------------+

INSERT INTO v VALUES(120),(80);

SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
|   200.5000 |
+------------+

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_POP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         287.1875 |
| Esben   | SQL    |    43 |         287.1875 |
| Kaolin  | SQL    |    56 |         287.1875 |
| Tatiana | SQL    |    87 |         287.1875 |
| Chun    | Tuning |    73 |         582.0000 |
| Esben   | Tuning |    31 |         582.0000 |
| Kaolin  | Tuning |    88 |         582.0000 |
+---------+--------+-------+------------------+

See Also

VAR_SAMP

Syntax

VAR_SAMP(expr)

Description

Returns the sample variance of expr. That is, the denominator is the number of rows minus one.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VAR_SAMP() can be used as a window function.

VAR_SAMP() returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_SAMP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         382.9167 |
| Chun    | Tuning |    73 |         873.0000 |
| Esben   | SQL    |    43 |         382.9167 |
| Esben   | Tuning |    31 |         873.0000 |
| Kaolin  | SQL    |    56 |         382.9167 |
| Kaolin  | Tuning |    88 |         873.0000 |
| Tatiana | SQL    |    87 |         382.9167 |
+---------+--------+-------+------------------+

See Also

CHARSET

Syntax

CHARSET(str)

Description

Returns the character set of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set.

Examples

SELECT CHARSET('abc');
+----------------+
| CHARSET('abc') |
+----------------+
| latin1         |
+----------------+

SELECT CHARSET(CONVERT('abc' USING utf8));
+------------------------------------+
| CHARSET(CONVERT('abc' USING utf8)) |
+------------------------------------+
| utf8                               |
+------------------------------------+

SELECT CHARSET(USER());
+-----------------+
| CHARSET(USER()) |
+-----------------+
| utf8            |
+-----------------+

BUFFER

A synonym for ST_BUFFER.

CONVEXHULL

A synonym for ST_CONVEXHULL.

GEOMETRYCOLLECTION

Syntax

GeometryCollection(g1,g2,...)

Description

Constructs a WKB GeometryCollection. If any argument is not a well-formed WKB representation of a geometry, the return value is NULL.

Examples

CREATE TABLE gis_geometrycollection  (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
    (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')),
    (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))),
    (GeomFromText('GeometryCollection()')),
    (GeomFromText('GeometryCollection EMPTY'));

MULTILINESTRING

Syntax

MultiLineString(ls1,ls2,...)

Description

Constructs a WKB MultiLineString value using WKB LineString arguments. If any argument is not a WKB LineString, the return value is NULL.

Example

CREATE TABLE gis_multi_line (g MULTILINESTRING);
INSERT INTO gis_multi_line VALUES
 (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')),
 (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
 (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5),Point(5, 8),Point(21, 7))))));

MULTIPOINT

Syntax

MultiPoint(pt1,pt2,...)

Description

Constructs a WKB MultiPoint value using WKB Point arguments. If any argument is not a WKB Point, the return value is NULL.

Examples

SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )');

CREATE TABLE gis_multi_point (g MULTIPOINT);
INSERT INTO gis_multi_point VALUES
    (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')),
    (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
    (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10)))));

COERCIBILITY

Syntax

COERCIBILITY(str)

Description

Returns the collation coercibility value of the string argument. Coercibility defines what will be converted to what in case of collation conflict, with an expression with higher coercibility being converted to the collation of an expression with lower coercibility.

CoercibilityDescriptionExample
0ExplicitValue using a COLLATE clause
1No collationConcatenated strings using different collations
2ImplicitColumn value
3ConstantUSER() return value
4CoercibleLiteral string
5IgnorableNULL or derived from NULL

Examples

SELECT COERCIBILITY('abc' COLLATE latin1_swedish_ci);
+-----------------------------------------------+
| COERCIBILITY('abc' COLLATE latin1_swedish_ci) |
+-----------------------------------------------+
|                                             0 |
+-----------------------------------------------+

SELECT COERCIBILITY(USER());
+----------------------+
| COERCIBILITY(USER()) |
+----------------------+
|                    3 |
+----------------------+

SELECT COERCIBILITY('abc');
+---------------------+
| COERCIBILITY('abc') |
+---------------------+
|                   4 |
+---------------------+

CURRENT_ROLE

Syntax

CURRENT_ROLE, CURRENT_ROLE()

Description

Returns the current role name. This determines your access privileges. The return value is a string in the utf8 character set.

If there is no current role, NULL is returned.

The output of SELECT CURRENT_ROLE is equivalent to the contents of the ENABLED_ROLES Information Schema table.

USER() returns the combination of user and host used to login. CURRENT_USER() returns the account used to determine current connection's privileges.

Examples

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE staff;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff        |
+--------------+

CURRENT_USER

Syntax

CURRENT_USER, CURRENT_USER()

Description

Returns the user name and host name combination for the MariaDB account that the server used to authenticate the current client. This account determines your access privileges. The return value is a string in the utf8 character set.

The value of CURRENT_USER() can differ from the value of USER(). CURRENT_ROLE() returns the current active role.

Examples

shell> mysql --user="anonymous"

select user(),current_user();
+---------------------+----------------+
| user()              | current_user() |
+---------------------+----------------+
| anonymous@localhost | @localhost     |
+---------------------+----------------+

When calling CURRENT_USER() in a stored procedure, it returns the owner of the stored procedure, as defined with DEFINER.

See Also

DATABASE

Syntax

DATABASE()

Description

Returns the default (current) database name as a string in the utf8 character set. If there is no default database, DATABASE() returns NULL. Within a stored routine, the default database is the database that the routine is associated with, which is not necessarily the same as the database that is the default in the calling context.

SCHEMA() is a synonym for DATABASE().

To select a default database, the USE statement can be run. Another way to set the default database is specifying its name at mysql command line client startup.

Examples

SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| NULL       |
+------------+

USE test;
Database changed

SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| test       |
+------------+

DEFAULT

Syntax

DEFAULT(col_name)

Description

Returns the default value for a table column. If the column has no default value (and is not NULLABLE - NULLABLE fields have a NULL default), an error is returned.

For integer columns using AUTO_INCREMENT, 0 is returned.

When using DEFAULT as a value to set in an INSERT or UPDATE statement, you can use the bare keyword DEFAULT without the parentheses and argument to refer to the column in context. You can only use DEFAULT as a bare keyword if you are using it alone without a surrounding expression or function.

Examples

Select only non-default values for a column:

SELECT i FROM t WHERE i != DEFAULT(i);

Update values to be one greater than the default value:

UPDATE t SET i = DEFAULT(i)+1 WHERE i < 100;

When referring to the default value exactly in UPDATE or INSERT, you can omit the argument:

INSERT INTO t (i) VALUES (DEFAULT);
UPDATE t SET i = DEFAULT WHERE i < 100;
CREATE OR REPLACE TABLE t (
  i INT NOT NULL AUTO_INCREMENT, 
  j INT NOT NULL, 
  k INT DEFAULT 3, 
  l INT NOT NULL DEFAULT 4, 
  m INT, 
  PRIMARY KEY (i)
);

DESC t;
+-------+---------+------+-----+---------+----------------+
| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+
| i     | int(11) | NO   | PRI | NULL    | auto_increment |
| j     | int(11) | NO   |     | NULL    |                |
| k     | int(11) | YES  |     | 3       |                |
| l     | int(11) | NO   |     | 4       |                |
| m     | int(11) | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+

INSERT INTO t (j) VALUES (1);
INSERT INTO t (j,m) VALUES (2,2);
INSERT INTO t (j,l,m) VALUES (3,3,3);

SELECT * FROM t;
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
| 3 | 3 |    3 | 3 |    3 |
+---+---+------+---+------+

SELECT DEFAULT(i), DEFAULT(k), DEFAULT (l), DEFAULT(m) FROM t;
+------------+------------+-------------+------------+
| DEFAULT(i) | DEFAULT(k) | DEFAULT (l) | DEFAULT(m) |
+------------+------------+-------------+------------+
|          0 |          3 |           4 |       NULL |
|          0 |          3 |           4 |       NULL |
|          0 |          3 |           4 |       NULL |
+------------+------------+-------------+------------+

SELECT DEFAULT(i), DEFAULT(k), DEFAULT (l), DEFAULT(m), DEFAULT(j)  FROM t;
ERROR 1364 (HY000): Field 'j' doesn't have a default value

SELECT * FROM t WHERE i = DEFAULT(i);
Empty set (0.001 sec)

SELECT * FROM t WHERE j = DEFAULT(j);
ERROR 1364 (HY000): Field 'j' doesn't have a default value

SELECT * FROM t WHERE k = DEFAULT(k);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
| 3 | 3 |    3 | 3 |    3 |
+---+---+------+---+------+

SELECT * FROM t WHERE l = DEFAULT(l);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
+---+---+------+---+------+

SELECT * FROM t WHERE m = DEFAULT(m);
Empty set (0.001 sec)

SELECT * FROM t WHERE m <=> DEFAULT(m);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
+---+---+------+---+------+

See Also

POINT

Syntax

Point(x,y)

Description

Constructs a WKB Point using the given coordinates.

Examples

SET @g = ST_GEOMFROMTEXT('Point(1 1)');

CREATE TABLE gis_point  (g POINT);
INSERT INTO gis_point VALUES
    (PointFromText('POINT(10 10)')),
    (PointFromText('POINT(20 10)')),
    (PointFromText('POINT(20 20)')),
    (PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));

PointOnSurface

A synonym for ST_PointOnSurface.

ST_INTERSECTION

Syntax

ST_INTERSECTION(g1,g2)

Description

Returns a geometry that is the intersection, or shared portion, of geometry g1 and geometry g2.

Examples

SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 1, 0 2)');

SELECT ASTEXT(ST_INTERSECTION(@g1,@g2));
+----------------------------------+
| ASTEXT(ST_INTERSECTION(@g1,@g2)) |
+----------------------------------+
| POINT(2 1)                       |
+----------------------------------+

ST_POINTONSURFACE

MariaDB starting with 10.1.2

ST_POINTONSURFACE() was introduced in MariaDB 10.1.2

Syntax

ST_PointOnSurface(g)
PointOnSurface(g)

Description

Given a geometry, returns a POINT guaranteed to intersect a surface. However, see MDEV-7514.

ST_PointOnSurface() and PointOnSurface() are synonyms.

BINLOG

Syntax

BINLOG 'str'

Description

BINLOG is an internal-use statement. It is generated by the mariadb-binlog/mysqlbinlog program as the printable representation of certain events in binary log files. The 'str' value is a base 64-encoded string the that server decodes to determine the data change indicated by the corresponding event. This statement requires the SUPER privilege (<= MariaDB 10.5.1) or theBINLOG REPLAY privilege (>= MariaDB 10.5.2).

See also

DECODE_HISTOGRAM

Syntax

DECODE_HISTOGRAM(hist_type,histogram)

Description

Returns a string of comma separated numeric values corresponding to a probability distribution represented by the histogram of type hist_type (SINGLE_PREC_HB or DOUBLE_PREC_HB). The hist_type and histogram would be commonly used from the mysql.column_stats table.

See Histogram Based Statistics for details.

Examples

CREATE TABLE origin (
  i INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
  v INT UNSIGNED NOT NULL
);

INSERT INTO origin(v) VALUES 
  (1),(2),(3),(4),(5),(10),(20),
  (30),(40),(50),(60),(70),(80),
  (90),(100),(200),(400),(800);

SET histogram_size=10,histogram_type=SINGLE_PREC_HB;

ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table       | Op      | Msg_type | Msg_text                                |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status   | Engine-independent statistics collected |
| test.origin | analyze | status   | OK                                      |
+-------------+---------+----------+-----------------------------------------+

SELECT db_name,table_name,column_name,hist_type,
  hex(histogram),decode_histogram(hist_type,histogram) 
  FROM mysql.column_stats WHERE db_name='test' and table_name='origin';
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type      | hex(histogram)       | decode_histogram(hist_type,histogram)                             |
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| test    | origin     | i           | SINGLE_PREC_HB | 0F2D3C5A7887A5C3D2F0 | 0.059,0.118,0.059,0.118,0.118,0.059,0.118,0.118,0.059,0.118,0.059 |
| test    | origin     | v           | SINGLE_PREC_HB | 000001060C0F161C1F7F | 0.000,0.000,0.004,0.020,0.024,0.012,0.027,0.024,0.012,0.376,0.502 |
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+

SET histogram_size=20,histogram_type=DOUBLE_PREC_HB;

ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table       | Op      | Msg_type | Msg_text                                |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status   | Engine-independent statistics collected |
| test.origin | analyze | status   | OK                                      |
+-------------+---------+----------+-----------------------------------------+

SELECT db_name,table_name,column_name,
  hist_type,hex(histogram),decode_histogram(hist_type,histogram) 
  FROM mysql.column_stats WHERE db_name='test' and table_name='origin';
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type      | hex(histogram)                           | decode_histogram(hist_type,histogram)                                                   |
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| test    | origin     | i           | DOUBLE_PREC_HB | 0F0F2D2D3C3C5A5A78788787A5A5C3C3D2D2F0F0 | 0.05882,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.05882 |
| test    | origin     | v           | DOUBLE_PREC_HB | 5200F600480116067E0CB30F1B16831CB81FD67F | 0.00125,0.00250,0.00125,0.01877,0.02502,0.01253,0.02502,0.02502,0.01253,0.37546,0.50063 |

FOUND_ROWS

Syntax

FOUND_ROWS()

Description

A SELECT statement may include a LIMIT clause to restrict the number of rows the server returns to the client. In some cases, it is desirable to know how many rows the statement would have returned without the LIMIT, but without running the statement again. To obtain this row count, include a SQL_CALC_FOUND_ROWS option in the SELECT statement, and then invoke FOUND_ROWS() afterwards.

You can also use FOUND_ROWS() to obtain the number of rows returned by a SELECT which does not contain a LIMIT clause. In this case you don't need to use the SQL_CALC_FOUND_ROWS option. This can be useful for example in a stored procedure.

Also, this function works with some other statements which return a resultset, including SHOW, DESC and HELP. For DELETE ... RETURNING you should use ROW_COUNT(). It also works as a prepared statement, or after executing a prepared statement.

Statements which don't return any results don't affect FOUND_ROWS() - the previous value will still be returned.

Warning: When used after a CALL statement, this function returns the number of rows selected by the last query in the procedure, not by the whole procedure.

Statements using the FOUND_ROWS() function are not safe for replication.

Examples

SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
...
| SPHINX             | YES     | Sphinx storage engine                                          | NO           | NO   | NO         |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
11 rows in set (0.01 sec)

SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
|           11 |
+--------------+

SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name WHERE id > 100 LIMIT 10;

SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
|           23 |
+--------------+

See Also

LOAD INDEX

Syntax

LOAD INDEX INTO CACHE
  tbl_index_list [, tbl_index_list] ...

tbl_index_list:
  tbl_name
    [[INDEX|KEY] (index_name[, index_name] ...)]
    [IGNORE LEAVES]

Description

The LOAD INDEX INTO CACHE statement preloads a table index into the key cache to which it has been assigned by an explicit CACHE INDEX statement, or into the default key cache otherwise. LOAD INDEX INTO CACHE is used only for MyISAM or Aria tables. Until MariaDB 5.3, it was not supported for tables having user-defined partitioning, but this limitation was removed in MariaDB 5.5.

The IGNORE LEAVES modifier causes only blocks for the nonleaf nodes of the index to be preloaded.

LAST_INSERT_ID

Syntax

LAST_INSERT_ID(), LAST_INSERT_ID(expr)

Description

LAST_INSERT_ID() (no arguments) returns the first automatically generated value successfully inserted for an AUTO_INCREMENT column as a result of the most recently executed INSERT statement. The value of LAST_INSERT_ID() remains unchanged if no rows are successfully inserted.

If one gives an argument to LAST_INSERT_ID(), then it will return the value of the expression and the next call to LAST_INSERT_ID() will return the same value. The value will also be sent to the client and can be accessed by the mysql_insert_id function.

For example, after inserting a row that generates an AUTO_INCREMENT value, you can get the value like this:

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                9 |
+------------------+

You can also use LAST_INSERT_ID() to delete the last inserted row:

DELETE FROM product WHERE id = LAST_INSERT_ID();

If no rows were successfully inserted, LAST_INSERT_ID() returns 0.

The value of LAST_INSERT_ID() will be consistent across all versions if all rows in the INSERT or UPDATE statement were successful.

The currently executing statement does not affect the value of LAST_INSERT_ID(). Suppose that you generate an AUTO_INCREMENT value with one statement, and then refer to LAST_INSERT_ID() in a multiple-row INSERT statement that inserts rows into a table with its own AUTO_INCREMENT column. The value of LAST_INSERT_ID() will remain stable in the second statement; its value for the second and later rows is not affected by the earlier row insertions. (However, if you mix references to LAST_INSERT_ID() and LAST_INSERT_ID(expr), the effect is undefined.)

If the previous statement returned an error, the value of LAST_INSERT_ID() is undefined. For transactional tables, if the statement is rolled back due to an error, the value of LAST_INSERT_ID() is left undefined. For manual ROLLBACK, the value of LAST_INSERT_ID() is not restored to that before the transaction; it remains as it was at the point of the ROLLBACK.

Within the body of a stored routine (procedure or function) or a trigger, the value of LAST_INSERT_ID() changes the same way as for statements executed outside the body of these kinds of objects. The effect of a stored routine or trigger upon the value of LAST_INSERT_ID() that is seen by following statements depends on the kind of routine:

  • If a stored procedure executes statements that change the value of LAST_INSERT_ID(), the new value will be seen by statements that follow the procedure call.
  • For stored functions and triggers that change the value, the value is restored when the function or trigger ends, so following statements will not see a changed value.

Examples

CREATE TABLE t (
  id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY, 
  f VARCHAR(1)) 
ENGINE = InnoDB;

INSERT INTO t(f) VALUES('a');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                1 |
+------------------+

INSERT INTO t(f) VALUES('b');

INSERT INTO t(f) VALUES('c');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                3 |
+------------------+

INSERT INTO t(f) VALUES('d'),('e');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                4 |
+------------------+

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
+----+------+

SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
|                 12 |
+--------------------+

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|               12 |
+------------------+

INSERT INTO t(f) VALUES('f');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                6 |
+------------------+

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
|  6 | f    |
+----+------+

SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
|                 12 |
+--------------------+

INSERT INTO t(f) VALUES('g');

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
|  6 | f    |
|  7 | g    |
+----+------+

See Also

PROCEDURE ANALYSE

Syntax

analyse([max_elements[,max_memory]])

Description

This procedure is defined in the sql/sql_analyse.cc file. It examines the result from a query and returns an analysis of the results that suggests optimal data types for each column. To obtain this analysis, append PROCEDURE ANALYSE to the end of a SELECT statement:

SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements,[max_memory]])

For example:

SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);

The results show some statistics for the values returned by the query, and propose an optimal data type for the columns. This can be helpful for checking your existing tables, or after importing new data. You may need to try different settings for the arguments so that PROCEDURE ANALYSE() does not suggest the ENUM data type when it is not appropriate.

The arguments are optional and are used as follows:

  • max_elements (default 256) is the maximum number of distinct values that analyse notices per column. This is used by analyse to check whether the optimal data type should be of type ENUM; if there are more than max_elements distinct values, then ENUM is not a suggested type.
  • max_memory (default 8192) is the maximum amount of memory that analyse should allocate per column while trying to find all distinct values.

See Also

SHOW FUNCTION CODE

Syntax

SHOW FUNCTION CODE func_name

Description

SHOW FUNCTION CODE shows a representation of the internal implementation of the stored function.

It is similar to SHOW PROCEDURE CODE but for stored functions.

DO

Syntax

DO expr [, expr] ...

Description

DO executes the expressions but does not return any results. In most respects, DO is shorthand for SELECT expr, ..., but has the advantage that it is slightly faster when you do not care about the result.

DO is useful primarily with functions that have side effects, such as RELEASE_LOCK().

LAST_VALUE

Syntax

LAST_VALUE(expr,[expr,...])
LAST_VALUE(expr) OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

LAST_VALUE() evaluates all expressions and returns the last.

This is useful together with setting user variables to a value with @var:=expr, for example when you want to get data of rows updated/deleted without having to do two queries against the table.

Since MariaDB 10.2.2, LAST_VALUE can be used as a window function.

Returns NULL if no last value exists.

Examples

CREATE TABLE t1 (a int, b int);
INSERT INTO t1 VALUES(1,10),(2,20);
DELETE FROM t1 WHERE a=1 AND last_value(@a:=a,@b:=b,1);
SELECT @a,@b;
+------+------+
| @a   | @b   |
+------+------+
|    1 |   10 |
+------+------+

As a window function:

CREATE TABLE t1 (
  pk int primary key,
  a int,
  b int,
  c char(10),
  d decimal(10, 3),
  e real
);

INSERT INTO t1 VALUES
( 1, 0, 1,    'one',    0.1,  0.001),
( 2, 0, 2,    'two',    0.2,  0.002),
( 3, 0, 3,    'three',  0.3,  0.003),
( 4, 1, 2,    'three',  0.4,  0.004),
( 5, 1, 1,    'two',    0.5,  0.005),
( 6, 1, 1,    'one',    0.6,  0.006),
( 7, 2, NULL, 'n_one',  0.5,  0.007),
( 8, 2, 1,    'n_two',  NULL, 0.008),
( 9, 2, 2,    NULL,     0.7,  0.009),
(10, 2, 0,    'n_four', 0.8,  0.010),
(11, 2, 10,   NULL,     0.9,  NULL);

SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
           LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
           FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
           LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;

+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 |         1 |       11 |         11 |        11 |
| 10 |         1 |       10 |         11 |        10 |
|  9 |         1 |        9 |         11 |         9 |
|  8 |         1 |        8 |         11 |         8 |
|  7 |         1 |        7 |         11 |         7 |
|  6 |         1 |        6 |         11 |         6 |
|  5 |         1 |        5 |         11 |         5 |
|  4 |         1 |        4 |         11 |         4 |
|  3 |         1 |        3 |         11 |         3 |
|  2 |         1 |        2 |         11 |         2 |
|  1 |         1 |        1 |         11 |         1 |
+----+-----------+----------+------------+-----------+
CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);

SELECT i,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f
FROM t1;

+------+------+------+--------+--------+--------+--------+--------+--------+
| i    | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
|    1 |    1 |    2 |      1 |      2 |   NULL |   NULL |      2 |      3 |
|    2 |    2 |    3 |      1 |      3 |      1 |      1 |      3 |      4 |
|    3 |    3 |    4 |      2 |      4 |      1 |      2 |      4 |      5 |
|    4 |    4 |    5 |      3 |      5 |      2 |      3 |      5 |      6 |
|    5 |    5 |    6 |      4 |      6 |      3 |      4 |      6 |      7 |
|    6 |    6 |    7 |      5 |      7 |      4 |      5 |      7 |      8 |
|    7 |    7 |    8 |      6 |      8 |      5 |      6 |      8 |      9 |
|    8 |    8 |    9 |      7 |      9 |      6 |      7 |      9 |     10 |
|    9 |    9 |   10 |      8 |     10 |      7 |      8 |     10 |     10 |
|   10 |   10 |   10 |      9 |     10 |      8 |      9 |   NULL |   NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+

See Also

ROW_COUNT

Syntax

ROW_COUNT()

Description

ROW_COUNT() returns the number of rows updated, inserted or deleted by the preceding statement. This is the same as the row count that the mysql client displays and the value from the mysql_affected_rows() C API function.

Generally:

  • For statements which return a result set (such as SELECT, SHOW, DESC or HELP), returns -1, even when the result set is empty. This is also true for administrative statements, such as OPTIMIZE.
  • For DML statements other than SELECT and for ALTER TABLE, returns the number of affected rows.
  • For DDL statements (including TRUNCATE) and for other statements which don't return any result set (such as USE, DO, SIGNAL or DEALLOCATE PREPARE), returns 0.

For UPDATE, affected rows is by default the number of rows that were actually changed. If the CLIENT_FOUND_ROWS flag to mysql_real_connect() is specified when connecting to mysqld, affected rows is instead the number of rows matched by the WHERE clause.

For REPLACE, deleted rows are also counted. So, if REPLACE deletes a row and adds a new row, ROW_COUNT() returns 2.

For INSERT ... ON DUPLICATE KEY, updated rows are counted twice. So, if INSERT adds a new rows and modifies another row, ROW_COUNT() returns 3.

ROW_COUNT() does not take into account rows that are not directly deleted/updated by the last statement. This means that rows deleted by foreign keys or triggers are not counted.

Warning: You can use ROW_COUNT() with prepared statements, but you need to call it after EXECUTE, not after DEALLOCATE PREPARE, because the row count for allocate prepare is always 0.

Warning: When used after a CALL statement, this function returns the number of rows affected by the last statement in the procedure, not by the whole procedure.

Warning: After INSERT DELAYED, ROW_COUNT() returns the number of the rows you tried to insert, not the number of the successful writes.

This information can also be found in the diagnostics area.

Statements using the ROW_COUNT() function are not safe for replication.

Examples

CREATE TABLE t (A INT);

INSERT INTO t VALUES(1),(2),(3);

SELECT ROW_COUNT();
+-------------+
| ROW_COUNT() |
+-------------+
|           3 |
+-------------+

DELETE FROM t WHERE A IN(1,2);

SELECT ROW_COUNT(); 
+-------------+
| ROW_COUNT() |
+-------------+
|           2 |
+-------------+

Example with prepared statements:

SET @q = 'INSERT INTO t VALUES(1),(2),(3);';

PREPARE stmt FROM @q;

EXECUTE stmt;
Query OK, 3 rows affected (0.39 sec)
Records: 3  Duplicates: 0  Warnings: 0

SELECT ROW_COUNT();
+-------------+
| ROW_COUNT() |
+-------------+
|           3 |
+-------------+

See Also

DUAL

Description

You are allowed to specify DUAL as a dummy table name in situations where no tables are referenced, such as the following SELECT statement:

SELECT 1 + 1 FROM DUAL;
+-------+
| 1 + 1 |
+-------+
|     2 |
+-------+

DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MariaDB ignores the clauses. MariaDB does not require FROM DUAL if no tables are referenced.

FROM DUAL could be used when you only SELECT computed values, but require a WHERE clause, perhaps to test that a script correctly handles empty resultsets:

SELECT 1 FROM DUAL WHERE FALSE;
Empty set (0.00 sec)

See Also

FOR UPDATE

InnoDB supports row-level locking. Selected rows can be locked using LOCK IN SHARE MODE or FOR UPDATE. In both cases, a lock is acquired on the rows read by the query, and it will be released when the current transaction is committed.

The FOR UPDATE clause of SELECT applies only when autocommit is set to 0 or the SELECT is enclosed in a transaction. A lock is acquired on the rows, and other transactions are prevented from writing the rows, acquire locks, and from reading them (unless their isolation level is READ UNCOMMITTED).

If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect.

If the isolation level is set to SERIALIZABLE, all plain SELECT statements are converted to SELECT ... LOCK IN SHARE MODE.

Example

SELECT * FROM trans WHERE period=2001 FOR UPDATE;

See Also

USER

Syntax

USER()

Description

Returns the current MariaDB user name and host name, given when authenticating to MariaDB, as a string in the utf8 character set.

Note that the value of USER() may differ from the value of CURRENT_USER(), which is the user used to authenticate the current client. CURRENT_ROLE() returns the current active role.

SYSTEM_USER() and SESSION_USER are synonyms for USER().

Statements using the USER() function or one of its synonyms are not safe for statement level replication.

Examples

shell> mysql --user="anonymous"

SELECT USER(),CURRENT_USER();
+---------------------+----------------+
| USER()              | CURRENT_USER() |
+---------------------+----------------+
| anonymous@localhost | @localhost     |
+---------------------+----------------+

To select only the IP address, use SUBSTRING_INDEX(),

SELECT SUBSTRING_INDEX(USER(), '@', -1);
+----------------------------------+
| SUBSTRING_INDEX(USER(), '@', -1) |
+----------------------------------+
| 192.168.0.101                    |
+----------------------------------+

See Also

VERSION

Syntax

VERSION()

Description

Returns a string that indicates the MariaDB server version. The string uses the utf8 character set.

Examples

SELECT VERSION();
+----------------+
| VERSION()      |
+----------------+
| 10.4.7-MariaDB |
+----------------+

The VERSION() string may have one or more of the following suffixes:

SuffixDescription
-embeddedThe server is an embedded server (libmysqld).
-logGeneral logging, slow logging or binary (replication) logging is enabled.
-debugThe server is compiled for debugging.
-valgrind The server is compiled to be instrumented with valgrind.

Changing the Version String

Some old legacy code may break because they are parsing the VERSION string and expecting a MySQL string or a simple version string like Joomla til API17, see MDEV-7780.

From MariaDB 10.2, one can fool these applications by setting the version string from the command line or the my.cnf files with --version=....

Not Equal Operator: !=

Syntax

<>, !=

Description

Not equal operator. Evaluates both SQL expressions and returns 1 if they are not equal and 0 if they are equal, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) != (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a != t2.x) OR (t1.b != t2.y)
FROM t1 INNER JOIN t2;

Examples

SELECT '.01' <> '0.01';
+-----------------+
| '.01' <> '0.01' |
+-----------------+
|               1 |
+-----------------+

SELECT .01 <> '0.01';
+---------------+
| .01 <> '0.01' |
+---------------+
|             0 |
+---------------+

SELECT 'zapp' <> 'zappp';
+-------------------+
| 'zapp' <> 'zappp' |
+-------------------+
|                 1 |
+-------------------+

<=>

Syntax

<=>

Description

NULL-safe equal operator. It performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.

a <=> b is equivalent to a = b OR (a IS NULL AND b IS NULL).

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) <=> (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a <=> t2.x) AND (t1.b <=> t2.y)
FROM t1 INNER JOIN t2;

See also NULL Values in MariaDB.

Examples

SELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL;
+---------+---------------+------------+
| 1 <=> 1 | NULL <=> NULL | 1 <=> NULL |
+---------+---------------+------------+
|       1 |             1 |          0 |
+---------+---------------+------------+

SELECT 1 = 1, NULL = NULL, 1 = NULL;
+-------+-------------+----------+
| 1 = 1 | NULL = NULL | 1 = NULL |
+-------+-------------+----------+
|     1 |        NULL |     NULL |
+-------+-------------+----------+

=

Syntax

left_expr = right_expr

Description

Equal operator. Evaluates both SQL expressions and returns 1 if they are equal, 0 if they are not equal, or NULL if either expression is NULL. If the expressions return different data types (for example, a number and a string), a type conversion is performed.

When used in row comparisons these two queries are synonymous and return the same results:

SELECT (t1.a, t1.b) = (t2.x, t2.y) FROM t1 INNER JOIN t2;

SELECT (t1.a = t2.x) AND (t1.b = t2.y) FROM t1 INNER JOIN t2;

To perform a NULL-safe comparison, use the <=> operator.

= can also be used as an assignment operator.

Examples

SELECT 1 = 0;
+-------+
| 1 = 0 |
+-------+
|     0 |
+-------+

SELECT '0' = 0;
+---------+
| '0' = 0 |
+---------+
|       1 |
+---------+

SELECT '0.0' = 0;
+-----------+
| '0.0' = 0 |
+-----------+
|         1 |
+-----------+

SELECT '0.01' = 0;
+------------+
| '0.01' = 0 |
+------------+
|          0 |
+------------+

SELECT '.01' = 0.01;
+--------------+
| '.01' = 0.01 |
+--------------+
|            1 |
+--------------+

SELECT (5 * 2) = CONCAT('1', '0');
+----------------------------+
| (5 * 2) = CONCAT('1', '0') |
+----------------------------+
|                          1 |
+----------------------------+

SELECT 1 = NULL;
+----------+
| 1 = NULL |
+----------+
|     NULL |
+----------+

SELECT NULL = NULL;
+-------------+
| NULL = NULL |
+-------------+
|        NULL |
+-------------+

HANDLER Commands

Syntax

HANDLER tbl_name OPEN [ [AS] alias]
HANDLER tbl_name READ index_name { = | >= | <= | < } (value1,value2,...)
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ index_name { FIRST | NEXT | PREV | LAST }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ { FIRST | NEXT }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name CLOSE

Description

The HANDLER statement provides direct access to table storage engine interfaces for key lookups and key or table scans. It is available for at least Aria, Memory, MyISAM and InnoDB tables (and should work with most 'normal' storage engines, but not with system tables, MERGE or views).

HANDLER ... OPEN opens a table, allowing it to be accessible to subsequent HANDLER ... READ statements. The table can either be opened using an alias (which must then be used by HANDLER ... READ, or a table name.

The table object is only closed when HANDLER ... CLOSE is called by the session, and is not shared by other sessions.

Prepared statements work with HANDLER READ, which gives a much higher performance (50% speedup) as there is no parsing and all data is transformed in binary (without conversions to text, as with the normal protocol).

The HANDLER command does not work with partitioned tables.

Key Lookup

A key lookup is started with:

HANDLER tbl_name READ index_name { = | >= | <= | < }  (value,value) [LIMIT...]

The values stands for the value of each of the key columns. For most key types (except for HASH keys in MEMORY storage engine) you can use a prefix subset of it's columns.

If you are using LIMIT, then in case of >= or > then there is an implicit NEXT implied, while if you are using <= or < then there is an implicit PREV implied.

After the initial read, you can use

HANDLER tbl_name READ index_name NEXT [ LIMIT ... ]
or
HANDLER tbl_name READ index_name PREV [ LIMIT ... ]

to scan the rows in key order.

Note that the row order is not defined for keys with duplicated values and will vary from engine to engine.

Key Scans

You can scan a table in key order by doing:

HANDLER tbl_name READ index_name FIRST [ LIMIT ... ]
HANDLER tbl_name READ index_name NEXT  [ LIMIT ... ]

or, if the handler supports backwards key scans (most do):

HANDLER tbl_name READ index_name LAST [ LIMIT ... ]
HANDLER tbl_name READ index_name PREV [ LIMIT ... ]

Table Scans

You can scan a table in row order by doing:

HANDLER tbl_name READ FIRST [ LIMIT ... ]
HANDLER tbl_name READ NEXT  [ LIMIT ... ]

Limitations

As this is a direct interface to the storage engine, some limitations may apply for what you can do and what happens if the table changes. Here follows some of the common limitations:

Finding 'Old Rows'

HANDLER READ is not transaction safe, consistent or atomic. It's ok for the storage engine to returns rows that existed when you started the scan but that were later deleted. This can happen as the storage engine may cache rows as part of the scan from a previous read.

You may also find rows committed since the scan originally started.

Invisible Columns

HANDLER ... READ also reads the data of invisible-columns.

System-Versioned Tables

HANDLER ... READ reads everything from system-versioned tables, and so includes row_start and row_end fields, as well as all rows that have since been deleted or changed, including when history partitions are used.

Other Limitations

  • If you do an ALTER TABLE, all your HANDLER's for that table are automatically closed.
  • If you do an ALTER TABLE for a table that is used by some other connection with HANDLER, the ALTER TABLE will wait for the HANDLER to be closed.
  • For HASH keys, you must use all key parts when searching for a row.
  • For HASH keys, you can't do a key scan of all values. You can only find all rows with the same key value.
  • While each HANDLER READ command is atomic, if you do a scan in many steps, then some engines may give you error 1020 if the table changed between the commands. Please refer to the specific engine handler page if this happens.

Error Codes

  • Error 1031 (ER_ILLEGAL_HA) Table storage engine for 't1' doesn't have this option
    • If you get this for HANDLER OPEN it means the storage engine doesn't support HANDLER calls.
    • If you get this for HANDLER READ it means you are trying to use an incomplete HASH key.
  • Error 1020 (ER_CHECKREAD) Record has changed since last read in table '...'
    • This means that the table changed between two reads and the handler can't handle this case for the given scan.

See Also

LOCK IN SHARE MODE

InnoDB supports row-level locking. Selected rows can be locked using LOCK IN SHARE MODE or FOR UPDATE. In both cases, a lock is acquired on the rows read by the query, and it will be released when the current transaction is committed.

When LOCK IN SHARE MODE is specified in a SELECT statement, MariaDB will wait until all transactions that have modified the rows are committed. Then, a write lock is acquired. All transactions can read the rows, but if they want to modify them, they have to wait until your transaction is committed.

If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect.

See Also

PROCEDURE

The PROCEDURE clause of SELECT passes the whole result set to a Procedure which will process it. These Procedures are not Stored Procedures, and can only be written in the C language, so it is necessary to recompile the server.

Currently, the only available procedure is ANALYSE, which examines the resultset and suggests the optimal datatypes for each column. It is defined in the sql/sql_analyse.cc file, and can be used as an example to create more Procedures.

This clause cannot be used in a view's definition.

See Also

>

Syntax

>

Description

Greater than operator. Evaluates both SQL expressions and returns 1 if the left value is greater than the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) > (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b > t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 > 2;
+-------+
| 2 > 2 |
+-------+
|     0 |
+-------+

SELECT 'b' > 'a';
+-----------+
| 'b' > 'a' |
+-----------+
|         1 |
+-----------+

>=

Syntax

>=

Description

Greater than or equal operator. Evaluates both SQL expressions and returns 1 if the left value is greater than or equal to the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) >= (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b >= t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 >= 2;
+--------+
| 2 >= 2 |
+--------+
|      1 |
+--------+

SELECT 'A' >= 'a';
+------------+
| 'A' >= 'a' |
+------------+
|          1 |
+------------+

COALESCE

Syntax

COALESCE(value,...)

Description

Returns the first non-NULL value in the list, or NULL if there are no non-NULL values. At least one parameter must be passed.

The function is useful when substituting a default value for null values when displaying data.

See also NULL Values in MariaDB.

Examples

SELECT COALESCE(NULL,1);
+------------------+
| COALESCE(NULL,1) |
+------------------+
|                1 |
+------------------+
SELECT COALESCE(NULL,NULL,NULL);
+--------------------------+
| COALESCE(NULL,NULL,NULL) |
+--------------------------+
|                     NULL |
+--------------------------+

When two arguments are given, COALESCE() is the same as IFNULL():

SET @a=NULL, @b=1;

SELECT COALESCE(@a, @b), IFNULL(@a, @b);
+------------------+----------------+
| COALESCE(@a, @b) | IFNULL(@a, @b) |
+------------------+----------------+
|                1 |              1 |
+------------------+----------------+

Hex type confusion:

CREATE TABLE t1 (a INT, b VARCHAR(10));
INSERT INTO t1 VALUES (0x31, 0x61),(COALESCE(0x31), COALESCE(0x61));

SELECT * FROM t1;
+------+------+
| a    | b    |
+------+------+
|   49 | a    |
|    1 | a    |
+------+------+

The reason for the differing results above is that when 0x31 is inserted directly to the column, it's treated as a number (see Hexadecimal Literals), while when 0x31 is passed to COALESCE(), it's treated as a string, because:

  • HEX values have a string data type by default.
  • COALESCE() has the same data type as the argument.

Substituting zero for NULL (in this case when the aggregate function returns NULL after finding no rows):

SELECT SUM(score) FROM student;
+------------+
| SUM(score) |
+------------+
|       NULL |
+------------+

SELECT COALESCE(SUM(score),0) FROM student;
+------------------------+
| COALESCE(SUM(score),0) |
+------------------------+
|                      0 |
+------------------------+

See also

IN

Syntax

expr IN (value,...)

Description

Returns 1 if expr is equal to any of the values in the IN list, else returns 0. If all values are constants, they are evaluated according to the type of expr and sorted. The search for the item then is done using a binary search. This means IN is very quick if the IN value list consists entirely of constants. Otherwise, type conversion takes place according to the rules described at Type Conversion, but applied to all the arguments.

If expr is NULL, IN always returns NULL. If at least one of the values in the list is NULL, and one of the comparisons is true, the result is 1. If at least one of the values in the list is NULL and none of the comparisons is true, the result is NULL.

Examples

SELECT 2 IN (0,3,5,7);
+----------------+
| 2 IN (0,3,5,7) |
+----------------+
|              0 |
+----------------+
SELECT 'wefwf' IN ('wee','wefwf','weg');
+----------------------------------+
| 'wefwf' IN ('wee','wefwf','weg') |
+----------------------------------+
|                                1 |
+----------------------------------+ 

Type conversion:

SELECT 1 IN ('1', '2', '3');
+----------------------+
| 1 IN ('1', '2', '3') |
+----------------------+
|                    1 |
+----------------------+
SELECT NULL IN (1, 2, 3);
+-------------------+
| NULL IN (1, 2, 3) |
+-------------------+
|              NULL |
+-------------------+

MariaDB [(none)]> SELECT 1 IN (1, 2, NULL);
+-------------------+
| 1 IN (1, 2, NULL) |
+-------------------+
|                 1 |
+-------------------+

MariaDB [(none)]> SELECT 5 IN (1, 2, NULL);
+-------------------+
| 5 IN (1, 2, NULL) |
+-------------------+
|              NULL |
+-------------------+

CONTAINS

Syntax

Contains(g1,g2)

Description

Returns 1 or 0 to indicate whether a geometry g1 completely contains geometry g2. CONTAINS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_CONTAINS() uses object shapes.

This tests the opposite relationship to Within().

DISJOINT

Syntax

Disjoint(g1,g2)

Description

Returns 1 or 0 to indicate whether g1 is spatially disjoint from (does not intersect) g2.

DISJOINT() tests the opposite relationship to INTERSECTS().

DISJOINT() is based on the original MySQL implementation and uses object bounding rectangles, while ST_DISJOINT() uses object shapes.

EQUALS

Syntax

Equals(g1,g2)

From MariaDB 10.2.3:

MBREQUALS(g1,g2)

Description

Returns 1 or 0 to indicate whether g1 is spatially equal to g2.

EQUALS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_EQUALS() uses object shapes.

From MariaDB 10.2.3, MBREQUALS is a synonym for Equals.

INTERSECTS

Syntax

INTERSECTS(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 spatially intersects geometry g2.

INTERSECTS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_INTERSECTS() uses object shapes.

INTERSECTS() tests the opposite relationship to DISJOINT().

OVERLAPS

Syntax

OVERLAPS(g1,g2)

Description

Returns 1 or 0 to indicate whether g1 spatially overlaps g2. The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries.

OVERLAPS() is based on the original MySQL implementation and uses object bounding rectangles, while ST_OVERLAPS() uses object shapes.

IS

Syntax

IS boolean_value

Description

Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN.

There is an important difference between using IS TRUE or comparing a value with TRUE using =. When using =, only 1 equals to TRUE. But when using IS TRUE, all values which are logically true (like a number > 1) return TRUE.

Examples

SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN;
+-----------+------------+-----------------+
| 1 IS TRUE | 0 IS FALSE | NULL IS UNKNOWN |
+-----------+------------+-----------------+
|         1 |          1 |               1 |
+-----------+------------+-----------------+

Difference between = and IS TRUE:

SELECT 2 = TRUE, 2 IS TRUE;
+----------+-----------+
| 2 = TRUE | 2 IS TRUE |
+----------+-----------+
|        0 |         1 |
+----------+-----------+

See Also

IS NOT

Syntax

IS NOT boolean_value

Description

Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN.

Examples

SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT UNKNOWN;
+------------------+------------------+---------------------+
| 1 IS NOT UNKNOWN | 0 IS NOT UNKNOWN | NULL IS NOT UNKNOWN |
+------------------+------------------+---------------------+
|                1 |                1 |                   0 |
+------------------+------------------+---------------------+
SELECT NULL IS NOT TRUE, NULL IS NOT FALSE;
+------------------+-------------------+
| NULL IS NOT TRUE | NULL IS NOT FALSE |
+------------------+-------------------+
|                1 |                 1 |
+------------------+-------------------+

IS NULL

Syntax

IS NULL

Description

Tests whether a value is NULL. See also NULL Values in MariaDB.

Examples

SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+-----------+-----------+--------------+
| 1 IS NULL | 0 IS NULL | NULL IS NULL |
+-----------+-----------+--------------+
|         0 |         0 |            1 |
+-----------+-----------+--------------+

Compatibility

Some ODBC applications use the syntax auto_increment_field IS NOT NULL to find the latest row that was inserted with an autogenerated key value. If your applications need this, you can set the sql_auto_is_null variable to 1.

SET @@sql_auto_is_null=1;
CREATE TABLE t1 (auto_increment_column INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
INSERT INTO t1 VALUES (NULL);
SELECT * FROM t1 WHERE auto_increment_column IS NULL;

+-----------------------+
| auto_increment_column |
+-----------------------+
|                     1 |
+-----------------------+

See also

LEAST

Syntax

LEAST(value1,value2,...)

Description

With two or more arguments, returns the smallest (minimum-valued) argument. The arguments are compared using the following rules:

  • If the return value is used in an INTEGER context or all arguments are integer-valued, they are compared as integers.
  • If the return value is used in a REAL context or all arguments are real-valued, they are compared as reals.
  • If any argument is a case-sensitive string, the arguments are compared as case-sensitive strings.
  • In all other cases, the arguments are compared as case-insensitive strings.

LEAST() returns NULL if any argument is NULL.

Examples

SELECT LEAST(2,0);
+------------+
| LEAST(2,0) |
+------------+
|          0 |
+------------+
SELECT LEAST(34.0,3.0,5.0,767.0);
+---------------------------+
| LEAST(34.0,3.0,5.0,767.0) |
+---------------------------+
|                       3.0 |
+---------------------------+
SELECT LEAST('B','A','C');
+--------------------+
| LEAST('B','A','C') |
+--------------------+
| A                  |
+--------------------+

NOT BETWEEN

Syntax

expr NOT BETWEEN min AND max

Description

This is the same as NOT (expr BETWEEN min AND max).

Note that the meaning of the alternative form NOT expr BETWEEN min AND max is affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag.

Examples

SELECT 1 NOT BETWEEN 2 AND 3;
+-----------------------+
| 1 NOT BETWEEN 2 AND 3 |
+-----------------------+
|                     1 |
+-----------------------+
SELECT 'b' NOT BETWEEN 'a' AND 'c';
+-----------------------------+
| 'b' NOT BETWEEN 'a' AND 'c' |
+-----------------------------+
|                           0 |
+-----------------------------+

NULL:

SELECT 1 NOT BETWEEN 1 AND NULL;
+--------------------------+
| 1 NOT BETWEEN 1 AND NULL |
+--------------------------+
|                     NULL |
+--------------------------+

NOT IN

Syntax

expr NOT IN (value,...)

Description

This is the same as NOT (expr IN (value,...)).

Examples

SELECT 2 NOT IN (0,3,5,7);
+--------------------+
| 2 NOT IN (0,3,5,7) |
+--------------------+
|                  1 |
+--------------------+
SELECT 'wefwf' NOT IN ('wee','wefwf','weg');
+--------------------------------------+
| 'wefwf' NOT IN ('wee','wefwf','weg') |
+--------------------------------------+
|                                    0 |
+--------------------------------------+
SELECT 1 NOT IN ('1', '2', '3');
+--------------------------+
| 1 NOT IN ('1', '2', '3') |
+--------------------------+
|                        0 |
+--------------------------+

NULL:

SELECT NULL NOT IN (1, 2, 3);
+-----------------------+
| NULL NOT IN (1, 2, 3) |
+-----------------------+
|                  NULL |
+-----------------------+

SELECT 1 NOT IN (1, 2, NULL);
+-----------------------+
| 1 NOT IN (1, 2, NULL) |
+-----------------------+
|                     0 |
+-----------------------+

SELECT 5 NOT IN (1, 2, NULL);
+-----------------------+
| 5 NOT IN (1, 2, NULL) |
+-----------------------+
|                  NULL |
+-----------------------+

ST_DIFFERENCE

Syntax

ST_DIFFERENCE(g1,g2)

Description

Returns a geometry representing the point set difference of the given geometry values.

Example

SET @g1 = POINT(10,10), @g2 = POINT(20,20);

SELECT ST_AsText(ST_Difference(@g1, @g2));
+------------------------------------+
| ST_AsText(ST_Difference(@g1, @g2)) |
+------------------------------------+
| POINT(10 10)                       |
+------------------------------------+

ST_DISTANCE

Syntax

ST_DISTANCE(g1,g2)

Description

Returns the distance between two geometries, or null if not given valid inputs.

Example

SELECT ST_Distance(POINT(1,2),POINT(2,2));
+------------------------------------+
| ST_Distance(POINT(1,2),POINT(2,2)) |
+------------------------------------+
|                                  1 |
+------------------------------------+

ST_LENGTH

Syntax

ST_LENGTH(ls)

Description

Returns as a double-precision number the length of the LineString value ls in its associated spatial reference.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT ST_LENGTH(ST_GeomFromText(@ls));
+---------------------------------+
| ST_LENGTH(ST_GeomFromText(@ls)) |
+---------------------------------+
|                2.82842712474619 |
+---------------------------------+

Parentheses

Parentheses are sometimes called precedence operators - this means that they can be used to change the other operator's precedence in an expression. The expressions that are written between parentheses are computed before the expressions that are written outside. Parentheses must always contain an expression (that is, they cannot be empty), and can be nested.

For example, the following expressions could return different results:

  • NOT a OR b
  • NOT (a OR b)

In the first case, NOT applies to a, so if a is FALSE or b is TRUE, the expression returns TRUE. In the second case, NOT applies to the result of a OR b, so if at least one of a or b is TRUE, the expression is TRUE.

When the precedence of operators is not intuitive, you can use parentheses to make it immediately clear for whoever reads the statement.

The precedence of the NOT operator can also be affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag.

Other uses

Parentheses must always be used to enclose subqueries.

Parentheses can also be used in a JOIN statement between multiple tables to determine which tables must be joined first.

Also, parentheses are used to enclose the list of parameters to be passed to built-in functions, user-defined functions and stored routines. However, when no parameter is passed to a stored procedure, parentheses are optional. For builtin functions and user-defined functions, spaces are not allowed between the function name and the open parenthesis, unless the IGNORE_SPACE SQL_MODE is set. For stored routines (and for functions if IGNORE_SPACE is set) spaces are allowed before the open parenthesis, including tab characters and new line characters.

Syntax errors

If there are more open parentheses than closed parentheses, the error usually looks like this:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MariaDB server version for the right syntax to use near '' a
t line 1

Note the empty string.

If there are more closed parentheses than open parentheses, the error usually looks like this:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MariaDB server version for the right syntax to use near ')'
at line 1

Note the quoted closed parenthesis.

ST_OVERLAPS

Syntax

ST_OVERLAPS(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 spatially overlaps geometry g2.

The term spatially overlaps is used if two geometries intersect and their intersection results in a geometry of the same dimension but not equal to either of the given geometries.

ST_OVERLAPS() uses object shapes, while OVERLAPS(), based on the original MySQL implementation, uses object bounding rectangles.

TOUCHES

Syntax

Touches(g1,g2)

Description

Returns 1 or 0 to indicate whether g1 spatially touches g2. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other.

TOUCHES() is based on the original MySQL implementation and uses object bounding rectangles, while ST_TOUCHES() uses object shapes.

CURRENT_DATE

Syntax

CURRENT_DATE, CURRENT_DATE()

Description

CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE().

CURRENT_TIME

Syntax

CURRENT_TIME
CURRENT_TIME([precision])

Description

CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().

See Also

CURRENT_TIMESTAMP

Syntax

CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])

Description

CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW().

See Also

CURTIME

Syntax

CURTIME([precision])

Description

Returns the current time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT CURTIME();
+-----------+
| CURTIME() |
+-----------+
| 12:45:39  |
+-----------+

SELECT CURTIME() + 0;
+---------------+
| CURTIME() + 0 |
+---------------+
| 124545.000000 |
+---------------+

With precision:

SELECT CURTIME(2);
+-------------+
| CURTIME(2)  |
+-------------+
| 09:49:08.09 |
+-------------+

See Also

DATE FUNCTION

Syntax

DATE(expr)

Description

Extracts the date part of the date or datetime expression expr.

Examples

SELECT DATE('2013-07-18 12:21:32');
+-----------------------------+
| DATE('2013-07-18 12:21:32') |
+-----------------------------+
| 2013-07-18                  |
+-----------------------------+

Error Handling

Until MariaDB 5.5.32, some versions of MariaDB returned 0000-00-00 when passed an invalid date. From 5.5.32, NULL is returned.

DAY

Syntax

DAY(date)

Description

DAY() is a synonym for DAYOFMONTH().

DAYOFYEAR

Syntax

DAYOFYEAR(date)

Description

Returns the day of the year for date, in the range 1 to 366.

Examples

SELECT DAYOFYEAR('2018-02-16');
+-------------------------+
| DAYOFYEAR('2018-02-16') |
+-------------------------+
|                      47 |
+-------------------------+

FROM_DAYS

Syntax

FROM_DAYS(N)

Description

Given a day number N, returns a DATE value. The day count is based on the number of days from the start of the standard calendar (0000-00-00).

The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar.

This is the converse of the TO_DAYS() function.

Examples

SELECT FROM_DAYS(730669);
+-------------------+
| FROM_DAYS(730669) |
+-------------------+
| 2000-07-03        |
+-------------------+

LOCALTIME

Syntax

LOCALTIME
LOCALTIME([precision])

Description

LOCALTIME and LOCALTIME() are synonyms for NOW().

See Also

LOCALTIMESTAMP

Syntax

LOCALTIMESTAMP
LOCALTIMESTAMP([precision])

Description

LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW().

See Also

MINUTE

Syntax

MINUTE(time)

Description

Returns the minute for time, in the range 0 to 59.

Examples

SELECT MINUTE('2013-08-03 11:04:03');
+-------------------------------+
| MINUTE('2013-08-03 11:04:03') |
+-------------------------------+
|                             4 |
+-------------------------------+

 SELECT MINUTE ('23:12:50');
+---------------------+
| MINUTE ('23:12:50') |
+---------------------+
|                  12 |
+---------------------+

CREATE FUNCTION UDF

Syntax

CREATE [OR REPLACE] [AGGREGATE] FUNCTION [IF NOT EXISTS] function_name
    RETURNS {STRING|INTEGER|REAL|DECIMAL}
    SONAME shared_library_name

Description

A user-defined function (UDF) is a way to extend MariaDB with a new function that works like a native (built-in) MariaDB function such as ABS() or CONCAT().

function_name is the name that should be used in SQL statements to invoke the function.

To create a function, you must have the INSERT privilege for the mysql database. This is necessary becauseCREATE FUNCTION adds a row to the mysql.func system table that records the function's name, type, and shared library name. If you do not have this table, you should run the mysql_upgrade command to create it.

UDFs need to be written in C, C++ or another language that uses C calling conventions, MariaDB needs to have been dynamically compiled, and your operating system must support dynamic loading.

For an example, see sql/udf_example.cc in the source tree. For a collection of existing UDFs see http://www.mysqludf.org/.

Statements making use of user-defined functions are not safe for replication.

For creating a stored function as opposed to a user-defined function, see CREATE FUNCTION.

For valid identifiers to use as function names, see Identifier Names.

RETURNS

The RETURNS clause indicates the type of the function's return value, and can be one of STRING, INTEGER, REAL or DECIMAL. DECIMAL functions currently return string values and should be written like STRING functions.

shared_library_name

shared_library_name is the basename of the shared object file that contains the code that implements the function. The file must be located in the plugin directory. This directory is given by the value of the plugin_dir system variable. Note that before MariaDB/MySQL 5.1, the shared object could be located in any directory that was searched by your system's dynamic linker.

AGGREGATE

Aggregate functions are summary functions such as SUM() and AVG().

MariaDB starting with 10.4

Aggregate UDF functions can be used as window functions.

OR REPLACE

MariaDB starting with 10.1.3

The OR REPLACE clause was added in MariaDB 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION name ...;

IF NOT EXISTS

MariaDB starting with 10.1.3

The IF NOT EXISTS clause was added in MariaDB 10.1.3

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified function already exists. Cannot be used together with OR REPLACE.

Upgrading a UDF

To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server.

Examples

CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)

OR REPLACE and IF NOT EXISTS:

CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
ERROR 1125 (HY000): Function 'jsoncontains_path' already exists

CREATE OR REPLACE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)

CREATE FUNCTION IF NOT EXISTS jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message                                     |
+-------+------+---------------------------------------------+
| Note  | 1125 | Function 'jsoncontains_path' already exists |
+-------+------+---------------------------------------------+

See Also

MONTH

Syntax

MONTH(date)

Description

Returns the month for date in the range 1 to 12 for January to December, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero month part.

Examples

SELECT MONTH('2019-01-03');
+---------------------+
| MONTH('2019-01-03') |
+---------------------+
|                   1 |
+---------------------+

SELECT MONTH('2019-00-03');
+---------------------+
| MONTH('2019-00-03') |
+---------------------+
|                   0 |
+---------------------+

MONTHNAME

Syntax

MONTHNAME(date)

Description

Returns the full name of the month for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

Examples

SELECT MONTHNAME('2019-02-03');
+-------------------------+
| MONTHNAME('2019-02-03') |
+-------------------------+
| February                |
+-------------------------+

Changing the locale:

SET lc_time_names = 'fr_CA';

SELECT MONTHNAME('2019-05-21');
+-------------------------+
| MONTHNAME('2019-05-21') |
+-------------------------+
| mai                     |
+-------------------------+

QUARTER

Syntax

QUARTER(date)

Description

Returns the quarter of the year for date, in the range 1 to 4. Returns 0 if month contains a zero value, or NULL if the given value is not otherwise a valid date (zero values are accepted).

Examples

SELECT QUARTER('2008-04-01');
+-----------------------+
| QUARTER('2008-04-01') |
+-----------------------+
|                     2 |
+-----------------------+

SELECT QUARTER('2019-00-01');
+-----------------------+
| QUARTER('2019-00-01') |
+-----------------------+
|                     0 |
+-----------------------+

SECOND

Syntax

SECOND(time)

Description

Returns the second for a given time (which can include microseconds), in the range 0 to 59, or NULL if not given a valid time value.

Examples

SELECT SECOND('10:05:03');
+--------------------+
| SECOND('10:05:03') |
+--------------------+
|                  3 |
+--------------------+

SELECT SECOND('10:05:01.999999');
+---------------------------+
| SECOND('10:05:01.999999') |
+---------------------------+
|                         1 |
+---------------------------+

DROP FUNCTION UDF

Syntax

DROP FUNCTION [IF EXISTS] function_name

Description

This statement drops the user-defined function (UDF) named function_name.

To drop a function, you must have the DELETE privilege for the mysql database. This is because DROP FUNCTION removes the row from the mysql.func system table that records the function's name, type and shared library name.

For dropping a stored function, see DROP FUNCTION.

Upgrading a UDF

To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server.

Examples

DROP FUNCTION jsoncontains_path;

IF EXISTS:

DROP FUNCTION jsoncontains_path;
ERROR 1305 (42000): FUNCTION test.jsoncontains_path does not exist

DROP FUNCTION IF EXISTS jsoncontains_path;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------------+
| Level | Code | Message                                        |
+-------+------+------------------------------------------------+
| Note  | 1305 | FUNCTION test.jsoncontains_path does not exist |
+-------+------+------------------------------------------------+

Creating User-Defined Functions

User-defined functions allow MariaDB to be extended with a new function that works like a native (built-in) MariaDB function such as ABS() or CONCAT(). There are alternative ways to add a new function: writing a native function (which requires modifying and compiling the server source code), or writing a stored function.

Statements making use of user-defined functions are not safe for replication.

Functions are written in C or C++, and to make use of them, the operating system must support dynamic loading.

Each new SQL function requires corresponding functions written in C/C++. In the list below, at least the main function - x() - and one other, are required. x should be replaced by the name of the function you are creating.

All functions need to be thread-safe, so not global or static variables that change can be allocated. Memory is allocated in x_init()/ and freed in x_deinit().

Simple Functions

x()

Required for all UDFs; this is where the results are calculated.

C/C++ typeSQL type
char *STRING
long longINTEGER
doubleREAL

DECIMAL functions return string values, and so should be written accordingly. It is not possible to create ROW functions.

x_init()

Initialization function for x(). Can be used for the following:

  • Check the number of arguments to X() (the SQL equivalent).
  • Verify the argument types, or to force arguments to be of a particular type after the function is called.
  • Specify whether the result can be NULL.
  • Specify the maximum result length.
  • For REAL functions, specify the maximum number of decimals for the result.
  • Allocate any required memory.

x_deinit()

De-initialization function for x(). Used to de-allocate memory that was allocated in x_init().

Description

Each time the SQL function X() is called:

  • MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called.
  • If there is no x_init() function, or it has been called and did not return an error, x() is then called once per row.
  • After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init().
  • See User-defined Functions Calling Sequences for more details on the functions.

Aggregate Functions

The following functions are required for aggregate functions, such as AVG() and SUM(). When using CREATE FUNCTION, the AGGREGATE keyword is required.

x_clear()

Used to reset the current aggregate, but without inserting the argument as the initial aggregate value for the new group.

x_add()

Used to add the argument to the current aggregate.

x_remove()

Starting from MariaDB 10.4, improves the support of window functions (so it is not obligatory to add it) and should remove the argument from the current aggregate.

Description

Each time the aggregate SQL function X() is called:

  • MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called.
  • If there is no x_init() function, or it has been called and did not return an error, x() is then called once per row.
  • After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init().
  • MariaDB will first call the C/C++ initialization function, x_init(), assuming it exists. All setup will be performed, and if it returns an error, the SQL statement is aborted and no further functions are called.
  • The table is sorted according to the GROUP BY expression.
  • x_clear() is called for the first row of each new group.
  • x_add() is called once per row for each row in the same group.
  • x() is called when the group changes, or after the last row, to get the aggregate result.
  • The latter three steps are repeated until all rows have been processed.
  • After all rows have finished processing, x_deinit() is called, if present, to clean up by de-allocating any memory that was allocated in x_init().

Examples

For an example, see sql/udf_example.cc in the source tree. For a collection of existing UDFs see https://github.com/mysqludf.

See Also

TIME Function

Syntax

TIME(expr)

Description

Extracts the time part of the time or datetime expression expr and returns it as a string.

Examples

SELECT TIME('2003-12-31 01:02:03');
+-----------------------------+
| TIME('2003-12-31 01:02:03') |
+-----------------------------+
| 01:02:03                    |
+-----------------------------+

SELECT TIME('2003-12-31 01:02:03.000123');
+------------------------------------+
| TIME('2003-12-31 01:02:03.000123') |
+------------------------------------+
| 01:02:03.000123                    |
+------------------------------------+

TIME_FORMAT

Syntax

TIME_FORMAT(time,format)

Description

This is used like the DATE_FORMAT() function, but the format string may contain format specifiers only for hours, minutes, and seconds. Other specifiers produce a NULL value or 0.

Examples

SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
+--------------------------------------------+
| TIME_FORMAT('100:00:00', '%H %k %h %I %l') |
+--------------------------------------------+
| 100 100 04 04 4                            |
+--------------------------------------------+

User-Defined Functions Calling Sequences

The functions described in Creating User-defined Functions are expanded on this page. They are declared as follows:

Simple Functions

x()

If x() returns an integer, it is declared as follows:

long long x(UDF_INIT *initid, UDF_ARGS *args,
              char *is_null, char *error);

If x() returns a string (DECIMAL functions also return string values), it is declared as follows:

char *x(UDF_INIT *initid, UDF_ARGS *args,
          char *result, unsigned long *length,
          char *is_null, char *error);

If x() returns a real, it is declared as follows:

double x(UDF_INIT *initid, UDF_ARGS *args,
              char *is_null, char *error);

x_init()

my_bool x_init(UDF_INIT *initid, UDF_ARGS *args, char *message);

x_deinit()

void x_deinit(UDF_INIT *initid);

Description

initid is a parameter passed to all three functions that points to a UDF_INIT structure, used for communicating information between the functions. Its structure members are:

  • my_bool maybe_null
    • maybe_null should be set to 1 if x_init can return a NULL value, Defaults to 1 if any arguments are declared maybe_null.
  • unsigned int decimals
    • Number of decimals after the decimal point. The default, if an explicit number of decimals is passed in the arguments to the main function, is the maximum number of decimals, so if 9.5, 9.55 and 9.555 are passed to the function, the default would be three (based on 9.555, the maximum). If there are no explicit number of decimals, the default is set to 31, or one more than the maximum for the DOUBLE, FLOAT and DECIMAL types. This default can be changed in the function to suit the actual calculation.
  • unsigned int max_length
    • Maximum length of the result. For integers, the default is 21. For strings, the length of the longest argument. For reals, the default is 13 plus the number of decimals indicated by initid->decimals. The length includes any signs or decimal points. Can also be set to 65KB or 16MB in order to return a BLOB. The memory remains unallocated, but this is used to decide on the data type to use if the data needs to be temporarily stored.
  • char *ptr
    • A pointer for use as required by the function. Commonly, initid->ptr is used to communicate allocated memory, with x_init() allocating the memory and assigning it to this pointer, x() using it, and x_deinit() de-allocating it.
  • my_bool const_item
    • Should be set to 1 in x_init() if x() always returns the same value, otherwise 0.

Aggregate Functions

x_clear()

x_clear() is a required function for aggregate functions, and is declared as follows:

void x_clear(UDF_INIT *initid, char *is_null, char *error);

It is called when the summary results need to be reset, that is at the beginning of each new group. but also to reset the values when there were no matching rows.

is_null is set to point to CHAR(0) before calling x_clear().

In the case of an error, you can store the value to which the error argument points (a single-byte variable, not a string string buffer) in the variable.

x_reset()

x_reset() is declared as follows:

void x_reset(UDF_INIT *initid, UDF_ARGS *args,
               char *is_null, char *error);

It is called on finding the first row in a new group. Should reset the summary variables, and then use UDF_ARGS as the first value in the group's internal summary value. The function is not required if the UDF interface uses x_clear().

x_add()

x_add() is declared as follows:

void x_add(UDF_INIT *initid, UDF_ARGS *args,
             char *is_null, char *error);

It is called for all rows belonging to the same group, and should be used to add the value in UDF_ARGS to the internal summary variable.

x_remove()

x_remove() was added in MariaDB 10.4 and is declared as follows (same as x_add()):

void x_remove(UDF_INIT* initid, UDF_ARGS* args,
               char* is_null, char *error );

It adds more efficient support of aggregate UDFs as window functions. x_remove() should "subtract" the row (reverse x_add()). In MariaDB 10.4 aggregate UDFs will work as WINDOW functions without x_remove() but it will not be so efficient.

If x_remove() supported (defined) detected automatically.

User-Defined Functions Security

The MariaDB server imposes a number of limitations on user-defined functions for security purposes.

  • The INSERT privilege for the mysql database is required to run CREATE FUNCTION, as a record will be added to the mysql.func-table.
  • The DELETE privilege for the mysql database is required to run DROP FUNCTION as the corresponding record will be removed from the mysql.func-table.
  • UDF object files can only be placed in the plugin directory, as specified by the value of the plugin_dir system variable.
  • At least one symbol, beyond the required x() - corresponding to an SQL function X()) - is required. These can be x_init(), x_deinit(), xxx_reset(), x_clear() and x_add() functions (see Creating User-defined Functions). The allow-suspicious-udfs mysqld option (by default unset) provides a workaround, permitting only one symbol to be used. This is not recommended, as it opens the possibility of loading shared objects that are not legitimate user-defined functions.

TIME_TO_SEC

Syntax

TIME_TO_SEC(time)

Description

Returns the time argument, converted to seconds.

The value returned by TIME_TO_SEC is of type DOUBLE. Before MariaDB 5.3 (and MySQL 5.6), the type was INT. The returned value preserves microseconds of the argument. See also Microseconds in MariaDB.

Examples

SELECT TIME_TO_SEC('22:23:00');
+-------------------------+
| TIME_TO_SEC('22:23:00') |
+-------------------------+
|                   80580 |
+-------------------------+
SELECT TIME_TO_SEC('00:39:38');
+-------------------------+
| TIME_TO_SEC('00:39:38') |
+-------------------------+
|                    2378 |
+-------------------------+
SELECT TIME_TO_SEC('09:12:55.2355');
+------------------------------+
| TIME_TO_SEC('09:12:55.2355') |
+------------------------------+
|                   33175.2355 |
+------------------------------+
1 row in set (0.000 sec)

UTC_DATE

Syntax

UTC_DATE, UTC_DATE()

Description

Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

Examples

SELECT UTC_DATE(), UTC_DATE() + 0;
+------------+----------------+
| UTC_DATE() | UTC_DATE() + 0 |
+------------+----------------+
| 2010-03-27 |       20100327 |
+------------+----------------+

UTC_TIME

Syntax

UTC_TIME
UTC_TIME([precision])

Description

Returns the current UTC time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT UTC_TIME(), UTC_TIME() + 0;
+------------+----------------+
| UTC_TIME() | UTC_TIME() + 0 |
+------------+----------------+
| 17:32:34   |  173234.000000 |
+------------+----------------+

With precision:

SELECT UTC_TIME(5);
+----------------+
| UTC_TIME(5)    |
+----------------+
| 07:52:50.78369 |
+----------------+

See Also

mysql.func Table

The mysql.func table stores information about user-defined functions (UDFs) created with the CREATE FUNCTION UDF statement.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.func table contains the following fields:

FieldTypeNullKeyDefaultDescription
namechar(64)NOPRIUDF name
rettinyint(1)NO0
dlchar(128)NOShared library name
typeenum('function','aggregate')NONULLType, either function or aggregate. Aggregate functions are summary functions such as SUM() and AVG().

Example

SELECT * FROM mysql.func;
+------------------------------+-----+--------------+-----------+
| name                         | ret | dl           | type      |
+------------------------------+-----+--------------+-----------+
| spider_direct_sql            |   2 | ha_spider.so | function  |
| spider_bg_direct_sql         |   2 | ha_spider.so | aggregate |
| spider_ping_table            |   2 | ha_spider.so | function  |
| spider_copy_tables           |   2 | ha_spider.so | function  |
| spider_flush_table_mon_cache |   2 | ha_spider.so | function  |
+------------------------------+-----+--------------+-----------+

AUTO_INCREMENT

Description

The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. When you insert a new record to the table (or upon adding an AUTO_INCREMENT attribute with the ALTER TABLE statement), and the auto_increment field is NULL or DEFAULT (in the case of an INSERT), the value will automatically be incremented. This also applies to 0, unless the NO_AUTO_VALUE_ON_ZERO SQL_MODE is enabled.

AUTO_INCREMENT columns start from 1 by default. The automatically generated value can never be lower than 0.

Each table can have only one AUTO_INCREMENT column. It must defined as a key (not necessarily the PRIMARY KEY or UNIQUE key). In some storage engines (including the default InnoDB), if the key consists of multiple columns, the AUTO_INCREMENT column must be the first column. Storage engines that permit the column to be placed elsewhere are Aria, MyISAM, MERGE, Spider, TokuDB, BLACKHOLE, FederatedX and Federated.

CREATE TABLE animals (
     id MEDIUMINT NOT NULL AUTO_INCREMENT,
     name CHAR(30) NOT NULL,
     PRIMARY KEY (id)
 );

INSERT INTO animals (name) VALUES
    ('dog'),('cat'),('penguin'),
    ('fox'),('whale'),('ostrich');
SELECT * FROM animals;
+----+---------+
| id | name    |
+----+---------+
|  1 | dog     |
|  2 | cat     |
|  3 | penguin |
|  4 | fox     |
|  5 | whale   |
|  6 | ostrich |
+----+---------+

SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.

CREATE TABLE t (id SERIAL, c CHAR(1)) ENGINE=InnoDB;

SHOW CREATE TABLE t \G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `c` char(1) DEFAULT NULL,
  UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Setting or Changing the Auto_Increment Value

You can use an ALTER TABLE statement to assign a new value to the auto_increment table option, or set the insert_id server system variable to change the next AUTO_INCREMENT value inserted by the current session.

LAST_INSERT_ID() can be used to see the last AUTO_INCREMENT value inserted by the current session.

ALTER TABLE animals AUTO_INCREMENT=8;

INSERT INTO animals (name) VALUES ('aardvark');

SELECT * FROM animals;
+----+-----------+
| id | name      |
+----+-----------+
|  1 | dog       |
|  2 | cat       |
|  3 | penguin   |
|  4 | fox       |
|  5 | whale     |
|  6 | ostrich   |
|  8 | aardvark  |
+----+-----------+

SET insert_id=12;

INSERT INTO animals (name) VALUES ('gorilla');

SELECT * FROM animals;
+----+-----------+
| id | name      |
+----+-----------+
|  1 | dog       |
|  2 | cat       |
|  3 | penguin   |
|  4 | fox       |
|  5 | whale     |
|  6 | ostrich   |
|  8 | aardvark  |
| 12 | gorilla   |
+----+-----------+

InnoDB

Until MariaDB 10.2.3, InnoDB used an auto-increment counter that is stored in memory. When the server restarts, the counter is re-initialized to the highest value used in the table, which cancels the effects of any AUTO_INCREMENT = N option in the table statements.

From MariaDB 10.2.4, this restriction has been lifted and AUTO_INCREMENT is persistent.

See also AUTO_INCREMENT Handling in InnoDB.

Setting Explicit Values

It is possible to specify a value for an AUTO_INCREMENT column. If the key is primary or unique, the value must not already exist in the key.

If the new value is higher than the current maximum value, the AUTO_INCREMENT value is updated, so the next value will be higher. If the new value is lower than the current maximum value, the AUTO_INCREMENT value remains unchanged.

The following example demonstrates these behaviors:

CREATE TABLE t (id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY) ENGINE = InnoDB;

INSERT INTO t VALUES (NULL);
SELECT id FROM t;
+----+
| id |
+----+
|  1 |
+----+

INSERT INTO t VALUES (10); -- higher value
SELECT id FROM t;
+----+
| id |
+----+
|  1 |
| 10 |
+----+

INSERT INTO t VALUES (2); -- lower value
INSERT INTO t VALUES (NULL); -- auto value
SELECT id FROM t;
+----+
| id |
+----+
|  1 |
|  2 |
| 10 |
| 11 |
+----+

The ARCHIVE storage engine does not allow to insert a value that is lower than the current maximum.

Missing Values

An AUTO_INCREMENT column normally has missing values. This happens because if a row is deleted, or an AUTO_INCREMENT value is explicitly updated, old values are never re-used. The REPLACE statement also deletes a row, and its value is wasted. With InnoDB, values can be reserved by a transaction; but if the transaction fails (for example, because of a ROLLBACK) the reserved value will be lost.

Thus AUTO_INCREMENT values can be used to sort results in a chronological order, but not to create a numeric sequence.

Replication

To make master-master or Galera safe to use AUTO_INCREMENT one should use the system variables auto_increment_increment and auto_increment_offset to generate unique values for each server.

CHECK Constraints, DEFAULT Values and Virtual Columns

MariaDB starting with 10.2.6

From MariaDB 10.2.6 auto_increment columns are no longer permitted in CHECK constraints, DEFAULT value expressions and virtual columns. They were permitted in earlier versions, but did not work correctly. See MDEV-11117.

Generating Auto_Increment Values When Adding the Attribute

CREATE OR REPLACE TABLE t1 (a INT);
INSERT t1 VALUES (0),(0),(0);
ALTER TABLE t1 MODIFY a INT NOT NULL AUTO_INCREMENT PRIMARY KEY;
SELECT * FROM t1;
+---+
| a |
+---+
| 1 |
| 2 |
| 3 |
+---+
CREATE OR REPLACE TABLE t1 (a INT);
INSERT t1 VALUES (5),(0),(8),(0);
ALTER TABLE t1 MODIFY a INT NOT NULL AUTO_INCREMENT PRIMARY KEY;
SELECT * FROM t1;
+---+
| a |
+---+
| 5 |
| 6 |
| 8 |
| 9 |
+---+

If the NO_AUTO_VALUE_ON_ZERO SQL_MODE is set, zero values will not be automatically incremented:

SET SQL_MODE='no_auto_value_on_zero';
CREATE OR REPLACE TABLE t1 (a INT);
INSERT t1 VALUES (3), (0);
ALTER TABLE t1 MODIFY a INT NOT NULL AUTO_INCREMENT PRIMARY KEY;
SELECT * FROM t1;
+---+
| a |
+---+
| 0 |
| 3 |
+---+

See Also

AsBinary

A synonym for ST_AsBinary().

AsWKB

A synonym for ST_AsBinary().

MLineFromWKB

Syntax

MLineFromWKB(wkb[,srid])
MultiLineStringFromWKB(wkb[,srid])

Description

Constructs a MULTILINESTRING value using its WKB representation and SRID.

MLineFromWKB() and MultiLineStringFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(MLineFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))'));

SELECT ST_AsText(MLineFromWKB(@g));
+--------------------------------------------------------+
| ST_AsText(MLineFromWKB(@g))                            |
+--------------------------------------------------------+
| MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48)) |
+--------------------------------------------------------+

BIGINT

Syntax

BIGINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]

Description

A large integer. The signed range is -9223372036854775808 to 9223372036854775807. The unsigned range is 0 to 18446744073709551615.

If a column has been set to ZEROFILL, all values will be prepended by zeros so that the BIGINT value contains a number of M digits.

Note: If the ZEROFILL attribute has been specified, the column will automatically become UNSIGNED.

For more details on the attributes, see Numeric Data Type Overview.

SERIAL is an alias for:

BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE

INT8 is a synonym for BIGINT.

Examples

CREATE TABLE bigints (a BIGINT,b BIGINT UNSIGNED,c BIGINT ZEROFILL);

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO bigints VALUES (-10,-10,-10);
ERROR 1264 (22003): Out of range value for column 'b' at row 1

INSERT INTO bigints VALUES (-10,10,-10);
ERROR 1264 (22003): Out of range value for column 'c' at row 1

INSERT INTO bigints VALUES (-10,10,10);

INSERT INTO bigints VALUES (9223372036854775808,9223372036854775808,9223372036854775808);
ERROR 1264 (22003): Out of range value for column 'a' at row 1

INSERT INTO bigints VALUES (9223372036854775807,9223372036854775808,9223372036854775808);

SELECT * FROM bigints;
+---------------------+---------------------+----------------------+
| a                   | b                   | c                    |
+---------------------+---------------------+----------------------+
|                 -10 |                  10 | 00000000000000000010 |
| 9223372036854775807 | 9223372036854775808 | 09223372036854775808 |
+---------------------+---------------------+----------------------+

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO bigints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.08 sec)
Warning (Code 1264): Out of range value for column 'b' at row 1
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO bigints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO bigints VALUES (-10,10,10);

INSERT INTO bigints VALUES (9223372036854775808,9223372036854775808,9223372036854775808);
Query OK, 1 row affected, 1 warning (0.07 sec)
Warning (Code 1264): Out of range value for column 'a' at row 1

INSERT INTO bigints VALUES (9223372036854775807,9223372036854775808,9223372036854775808);

SELECT * FROM bigints;
+---------------------+---------------------+----------------------+
| a                   | b                   | c                    |
+---------------------+---------------------+----------------------+
|                 -10 |                   0 | 00000000000000000000 |
|                 -10 |                  10 | 00000000000000000000 |
|                 -10 |                  10 | 00000000000000000010 |
| 9223372036854775807 | 9223372036854775808 | 09223372036854775808 |
| 9223372036854775807 | 9223372036854775808 | 09223372036854775808 |
+---------------------+---------------------+----------------------+

See Also

BINARY

This page describes the BINARY data type. For details about the operator, see Binary Operator.

Syntax

BINARY(M)

Description

The BINARY type is similar to the CHAR type, but stores binary byte strings rather than non-binary character strings. M represents the column length in bytes.

It contains no character set, and comparison and sorting are based on the numeric value of the bytes.

If the maximum length is exceeded, and SQL strict mode is not enabled , the extra characters will be dropped with a warning. If strict mode is enabled, an error will occur.

BINARY values are right-padded with 0x00 (the zero byte) to the specified length when inserted. The padding is not removed on select, so this needs to be taken into account when sorting and comparing, where all bytes are significant. The zero byte, 0x00 is less than a space for comparison purposes.

Examples

Inserting too many characters, first with strict mode off, then with it on:

CREATE TABLE bins (a BINARY(10));

INSERT INTO bins VALUES('12345678901');
Query OK, 1 row affected, 1 warning (0.04 sec)

SELECT * FROM bins;
+------------+
| a          |
+------------+
| 1234567890 |
+------------+

SET sql_mode='STRICT_ALL_TABLES';

INSERT INTO bins VALUES('12345678901');
ERROR 1406 (22001): Data too long for column 'a' at row 1

Sorting is performed with the byte value:

TRUNCATE bins;

INSERT INTO bins VALUES('A'),('B'),('a'),('b');

SELECT * FROM bins ORDER BY a;
+------+
| a    |
+------+
| A    |
| B    |
| a    |
| b    |
+------+

Using CAST to sort as a CHAR instead:

SELECT * FROM bins ORDER BY CAST(a AS CHAR);
+------+
| a    |
+------+
| a    |
| A    |
| b    |
| B    |
+------+

The field is a BINARY(10), so padding of two '\0's are inserted, causing comparisons that don't take this into account to fail:

TRUNCATE bins;

INSERT INTO bins VALUES('12345678');

SELECT a = '12345678', a = '12345678\0\0' from bins;
+----------------+--------------------+
| a = '12345678' | a = '12345678\0\0' |
+----------------+--------------------+
|              0 |                  1 |
+----------------+--------------------+

See Also

BIT

Syntax

BIT[(M)]

Description

A bit-field type. M indicates the number of bits per value, from 1 to 64. The default is 1 if M is omitted.

Bit values can be inserted with b'value' notation, where value is the bit value in 0's and 1's.

Bit fields are automatically zero-padded from the left to the full length of the bit, so for example in a BIT(4) field, '10' is equivalent to '0010'.

Bits are returned as binary, so to display them, either add 0, or use a function such as HEX, OCT or BIN to convert them.

Examples

CREATE TABLE b ( b1 BIT(8) );

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO b VALUES (b'11111111');

INSERT INTO b VALUES (b'01010101');

INSERT INTO b VALUES (b'1111111111111');
ERROR 1406 (22001): Data too long for column 'b1' at row 1

SELECT b1+0, HEX(b1), OCT(b1), BIN(b1) FROM b;
+------+---------+---------+----------+
| b1+0 | HEX(b1) | OCT(b1) | BIN(b1)  |
+------+---------+---------+----------+
|  255 | FF      | 377     | 11111111 |
|   85 | 55      | 125     | 1010101  |
+------+---------+---------+----------+

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO b VALUES (b'11111111'),(b'01010101'),(b'1111111111111');
Query OK, 3 rows affected, 1 warning (0.10 sec)
Records: 3  Duplicates: 0  Warnings: 1

SHOW WARNINGS;
+---------+------+---------------------------------------------+
| Level   | Code | Message                                     |
+---------+------+---------------------------------------------+
| Warning | 1264 | Out of range value for column 'b1' at row 3 |
+---------+------+---------------------------------------------+

SELECT b1+0, HEX(b1), OCT(b1), BIN(b1) FROM b;
+------+---------+---------+----------+
| b1+0 | HEX(b1) | OCT(b1) | BIN(b1)  |
+------+---------+---------+----------+
|  255 | FF      | 377     | 11111111 |
|   85 | 55      | 125     | 1010101  |
|  255 | FF      | 377     | 11111111 |
+------+---------+---------+----------+

MPointFromWKB

Syntax

MPointFromWKB(wkb[,srid])
MultiPointFromWKB(wkb[,srid])

Description

Constructs a MULTIPOINT value using its WKB representation and SRID.

MPointFromWKB() and MultiPointFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(MPointFromText('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )'));

SELECT ST_AsText(MPointFromWKB(@g));
+-----------------------------------------------------+
| ST_AsText(MPointFromWKB(@g))                        |
+-----------------------------------------------------+
| MULTIPOINT(1 1,2 2,5 3,7 2,9 3,8 4,6 6,6 9,4 9,1 5) |
+-----------------------------------------------------+

GeomCollFromWKB

A synonym for ST_GeomCollFromWKB.

GeometryCollectionFromWKB

A synonym for ST_GeomCollFromWKB.

GeometryFromWKB

A synonym for ST_GeomFromWKB.

GeomFromWKB

A synonym for ST_GeomFromWKB.

LineFromWKB

A synonym for ST_LineFromWKB.

LineStringFromWKB

A synonym for ST_LineFromWKB.

BLOB

Syntax

BLOB[(M)]

Description

A BLOB column with a maximum length of 65,535 (216 - 1) bytes. Each BLOB value is stored using a two-byte length prefix that indicates the number of bytes in the value.

An optional length M can be given for this type. If this is done, MariaDB creates the column as the smallest BLOB type large enough to hold values M bytes long.

BLOBS can also be used to store dynamic columns.

Before MariaDB 10.2.1, BLOB and TEXT columns could not be assigned a DEFAULT value. This restriction was lifted in MariaDB 10.2.1.

Indexing

MariaDB starting with 10.4

From MariaDB 10.4, it is possible to set a unique index on a column that uses the BLOB data type. In previous releases this was not possible, as the index would only guarantee the uniqueness of a fixed number of characters.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, BLOB is a synonym for LONGBLOB.

See Also

BOOLEAN

Syntax

BOOL, BOOLEAN

Description

These types are synonyms for TINYINT(1). A value of zero is considered false. Non-zero values are considered true.

However, the values TRUE and FALSE are merely aliases for 1 and 0. See Boolean Literals, as well as the IS operator for testing values against a boolean.

Examples

CREATE TABLE boo (i BOOLEAN);

DESC boo;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| i     | tinyint(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
SELECT IF(0, 'true', 'false');
+------------------------+
| IF(0, 'true', 'false') |
+------------------------+
| false                  |
+------------------------+

SELECT IF(1, 'true', 'false');
+------------------------+
| IF(1, 'true', 'false') |
+------------------------+
| true                   |
+------------------------+

SELECT IF(2, 'true', 'false');
+------------------------+
| IF(2, 'true', 'false') |
+------------------------+
| true                   |
+------------------------+

TRUE and FALSE as aliases for 1 and 0:

SELECT IF(0 = FALSE, 'true', 'false');

+--------------------------------+
| IF(0 = FALSE, 'true', 'false') |
+--------------------------------+
| true                           |
+--------------------------------+

SELECT IF(1 = TRUE, 'true', 'false');
+-------------------------------+
| IF(1 = TRUE, 'true', 'false') |
+-------------------------------+
| true                          |
+-------------------------------+

SELECT IF(2 = TRUE, 'true', 'false');
+-------------------------------+
| IF(2 = TRUE, 'true', 'false') |
+-------------------------------+
| false                         |
+-------------------------------+

SELECT IF(2 = FALSE, 'true', 'false');
+--------------------------------+
| IF(2 = FALSE, 'true', 'false') |
+--------------------------------+
| false                          |
+--------------------------------+

The last two statements display the results shown because 2 is equal to neither 1 nor 0.

See Also

CHAR

This article covers the CHAR data type. See CHAR Function for the function.

Syntax

[NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A fixed-length string that is always right-padded with spaces to the specified length when stored. M represents the column length in characters. The range of M is 0 to 255. If M is omitted, the length is 1.

CHAR(0) columns can contain 2 values: an empty string or NULL. Such columns cannot be part of an index. The CONNECT storage engine does not support CHAR(0).

Note: Trailing spaces are removed when CHAR values are retrieved unless the PAD_CHAR_TO_FULL_LENGTH SQL mode is enabled.

Before MariaDB 10.2, all collations were of type PADSPACE, meaning that CHAR (as well as VARCHAR and TEXT) values are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces.

If a unique index consists of a column where trailing pad characters are stripped or ignored, inserts into that column where values differ only by the number of trailing pad characters will result in a duplicate-key error.

Examples

Trailing spaces:

CREATE TABLE strtest (c CHAR(10));
INSERT INTO strtest VALUES('Maria   ');

SELECT c='Maria',c='Maria   ' FROM strtest;
+-----------+--------------+
| c='Maria' | c='Maria   ' |
+-----------+--------------+
|         1 |            1 |
+-----------+--------------+

SELECT c LIKE 'Maria',c LIKE 'Maria   ' FROM strtest;
+----------------+-------------------+
| c LIKE 'Maria' | c LIKE 'Maria   ' |
+----------------+-------------------+
|              1 |                 0 |
+----------------+-------------------+

NO PAD Collations

MariaDB starting with 10.2

NO PAD collations regard trailing spaces as normal characters. You can get a list of all NO PAD collations by querying the Information Schema Collations table, for example:

SELECT collation_name FROM information_schema.collations 
  WHERE collation_name LIKE "%nopad%";  
+------------------------------+
| collation_name               |
+------------------------------+
| big5_chinese_nopad_ci        |
| big5_nopad_bin               |
...

See Also

MultiLineStringFromWKB

A synonym for MLineFromWKB().

MultiPointFromWKB

A synonym for MPointFromWKB.

MultiPolygonFromWKB

Synonym for MPolyFromWKB.

PointFromWKB

A synonym for ST_PointFromWKB.

PolyFromWKB

A synonym for ST_PolyFromWKB.

PolygonFromWKB

A synonym for ST_PolyFromWKB.

ST_AsBinary

Syntax

ST_AsBinary(g)
AsBinary(g)
ST_AsWKB(g)
AsWKB(g)

Description

Converts a value in internal geometry format to its WKB representation and returns the binary result.

ST_AsBinary(), AsBinary(), ST_AsWKB() and AsWKB() are synonyms,

Examples

SET @poly = ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))');
SELECT ST_AsBinary(@poly);

SELECT ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly)));
+--------------------------------------------+
| ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly))) |
+--------------------------------------------+
| POLYGON((0 0,0 1,1 1,1 0,0 0))             |
+--------------------------------------------+

ST_AsWKB

A synonym for ST_AsBinary().

ST_GeometryCollectionFromWKB

A synonym for ST_GeomCollFromWKB.

ST_GeometryFromWKB

A synonym for ST_GeomFromWKB.

DATE

Syntax

DATE

Description

A date. The supported range is '1000-01-01' to '9999-12-31'. MariaDB displays DATE values in 'YYYY-MM-DD' format, but can be assigned dates in looser formats, including strings or numbers, as long as they make sense. These include a short year, YY-MM-DD, no delimiters, YYMMDD, or any other acceptable delimiter, for example YYYY/MM/DD. For details, see date and time literals.

'0000-00-00' is a permitted special value (zero-date), unless the NO_ZERO_DATE SQL_MODE is used. Also, individual components of a date can be set to 0 (for example: '2015-00-12'), unless the NO_ZERO_IN_DATE SQL_MODE is used. In many cases, the result of en expression involving a zero-date, or a date with zero-parts, is NULL. If the ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is in the range between 1 and 31, the date does not produce any error, even for months that have less than 31 days.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, DATE with a time portion is a synonym for DATETIME. See also mariadb_schema.

Examples

CREATE TABLE t1 (d DATE);

INSERT INTO t1 VALUES ("2010-01-12"), ("2011-2-28"), ('120314'),('13*04*21');

SELECT * FROM t1;
+------------+
| d          |
+------------+
| 2010-01-12 |
| 2011-02-28 |
| 2012-03-14 |
| 2013-04-21 |
+------------+

See Also

DATETIME

Syntax

DATETIME [(microsecond precision)]

Description

A date and time combination.

MariaDB displays DATETIME values in 'YYYY-MM-DD HH:MM:SS.ffffff' format, but allows assignment of values to DATETIME columns using either strings or numbers. For details, see date and time literals.

DATETIME columns also accept CURRENT_TIMESTAMP as the default value.

MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store DATETMEs using the same low-level format MySQL 5.6 uses. For more information, see Internal Format, below.

For storage requirements, see Data Type Storage Requirements.

Supported Values

MariaDB stores values that use the DATETIME data type in a format that supports values between 1000-01-01 00:00:00.000000 and 9999-12-31 23:59:59.999999.

MariaDB can also store microseconds with a precision between 0 and 6. If no microsecond precision is specified, then 0 is used by default.

MariaDB also supports '0000-00-00' as a special zero-date value, unless NO_ZERO_DATE is specified in the SQL_MODE. Similarly, individual components of a date can be set to 0 (for example: '2015-00-12'), unless NO_ZERO_DATE is specified in the SQL_MODE. In many cases, the result of en expression involving a zero-date, or a date with zero-parts, is NULL. If the ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is in the range between 1 and 31, the date does not produce any error, even for months that have less than 31 days.

Time Zones

If a column uses the DATETIME data type, then any inserted values are stored as-is, so no automatic time zone conversions are performed.

MariaDB also does not currently support time zone literals that contain time zone identifiers. See MDEV-11829 for more information.

MariaDB validates DATETIME literals against the session's time zone. For example, if a specific time range never occurred in a specific time zone due to daylight savings time, then DATETIME values within that range would be invalid for that time zone.

For example, daylight savings time started on March 10, 2019 in the US, so the time range between 02:00:00 and 02:59:59 is invalid for that day in US time zones:

SET time_zone = 'America/New_York';
Query OK, 0 rows affected (0.000 sec)

INSERT INTO timestamp_test VALUES ('2019-03-10 02:55:05');
ERROR 1292 (22007): Incorrect datetime value: '2019-03-10 02:55:05' for column `db1`.`timestamp_test`.`timestamp_test` at row 1

But that same time range is fine in other time zones, such as Coordinated Universal Time (UTC). For example:

SET time_zone = 'UTC';
Query OK, 0 rows affected (0.000 sec)

INSERT INTO timestamp_test VALUES ('2019-03-10 02:55:05');
Query OK, 1 row affected (0.002 sec)

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, DATE with a time portion is a synonym for DATETIME. See also mariadb_schema.

Internal Format

In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable.

Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format.

In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225).

For instance, if you have a DATETIME column in your table:

SHOW VARIABLES LIKE 'mysql56_temporal_format';

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON    |
+-------------------------+-------+

ALTER TABLE example_table MODIFY ts_col DATETIME;

When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one.

In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format.

Starting from MariaDB 10.5.1 columns with old temporal formats are marked with a /* mariadb-5.3 */ comment in the output of SHOW CREATE TABLE, SHOW COLUMNS, DESCRIBE statements, as well as in the COLUMN_TYPE column of the INFORMATION_SCHEMA.COLUMNS Table.

SHOW CREATE TABLE mariadb5312_datetime\G
*************************** 1. row ***************************
       Table: mariadb5312_datetime
Create Table: CREATE TABLE `mariadb5312_datetime` (
  `dt0` datetime /* mariadb-5.3 */ DEFAULT NULL,
  `dt6` datetime(6) /* mariadb-5.3 */ DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Examples

CREATE TABLE t1 (d DATETIME);

INSERT INTO t1 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"),
 ("2013-07-18 13:44:22.123456");

SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2011-03-11 00:00:00 |
| 2012-04-19 13:08:22 |
| 2013-07-18 13:44:22 |
+---------------------+
CREATE TABLE t2 (d DATETIME(6));

INSERT INTO t2 VALUES ("2011-03-11"), ("2012-04-19 13:08:22"),
 ("2013-07-18 13:44:22.123456");

SELECT * FROM t2;
+----------------------------+
| d                          |
+----------------------------+
| 2011-03-11 00:00:00.000000 |
| 2012-04-19 13:08:22.000000 |
| 2013-07-18 13:44:22.123456 |
+----------------------------++

Strings used in datetime context are automatically converted to datetime(6). If you want to have a datetime without seconds, you should use CONVERT(..,datetime).

SELECT CONVERT('2007-11-30 10:30:19',datetime);
+-----------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime) |
+-----------------------------------------+
| 2007-11-30 10:30:19                     |
+-----------------------------------------+

SELECT CONVERT('2007-11-30 10:30:19',datetime(6));
+--------------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime(6)) |
+--------------------------------------------+
| 2007-11-30 10:30:19.000000                 |
+--------------------------------------------+

See Also

ST_GeomFromWKB

Syntax

ST_GeomFromWKB(wkb[,srid])
ST_GeometryFromWKB(wkb[,srid])
GeomFromWKB(wkb[,srid])
GeometryFromWKB(wkb[,srid])

Description

Constructs a geometry value of any type using its WKB representation and SRID.

ST_GeomFromWKB(), ST_GeometryFromWKB(), GeomFromWKB() and GeometryFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(ST_LineFromText('LINESTRING(0 4, 4 6)'));

SELECT ST_AsText(ST_GeomFromWKB(@g));
+-------------------------------+
| ST_AsText(ST_GeomFromWKB(@g)) |
+-------------------------------+
| LINESTRING(0 4,4 6)           |
+-------------------------------+

ST_LineFromWKB

Syntax

ST_LineFromWKB(wkb[,srid])
LineFromWKB(wkb[,srid])
ST_LineStringFromWKB(wkb[,srid])
LineStringFromWKB(wkb[,srid])

Description

Constructs a LINESTRING value using its WKB representation and SRID.

ST_LineFromWKB(), LineFromWKB(), ST_LineStringFromWKB(), and LineStringFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(ST_LineFromText('LineString(0 4,4 6)'));

SELECT ST_AsText(ST_LineFromWKB(@g)) AS l;
+---------------------+
| l                   |
+---------------------+
| LINESTRING(0 4,4 6) |
+---------------------+

DECIMAL

Syntax

DECIMAL[(M[,D])] [SIGNED | UNSIGNED | ZEROFILL]

Description

A packed "exact" fixed-point number. M is the total number of digits (the precision) and D is the number of digits after the decimal point (the scale).

  • The decimal point and (for negative numbers) the "-" sign are not counted in M.
  • If D is 0, values have no decimal point or fractional part and on INSERT the value will be rounded to the nearest DECIMAL.
  • The maximum number of digits (M) for DECIMAL is 65.
  • The maximum number of supported decimals (D) is 30 before MariadB 10.2.1 and 38 afterwards.
  • If D is omitted, the default is 0. If M is omitted, the default is 10.

UNSIGNED, if specified, disallows negative values.

ZEROFILL, if specified, pads the number with zeros, up to the total number of digits specified by M.

All basic calculations (+, -, *, /) with DECIMAL columns are done with a precision of 65 digits.

For more details on the attributes, see Numeric Data Type Overview.

DEC, NUMERIC and FIXED are synonyms, as well as NUMBER in Oracle mode from MariaDB 10.3.

Examples

CREATE TABLE t1 (d DECIMAL UNSIGNED ZEROFILL);

INSERT INTO t1 VALUES (1),(2),(3),(4.0),(5.2),(5.7);
Query OK, 6 rows affected, 2 warnings (0.16 sec)
Records: 6  Duplicates: 0  Warnings: 2

Note (Code 1265): Data truncated for column 'd' at row 5
Note (Code 1265): Data truncated for column 'd' at row 6

SELECT * FROM t1;
+------------+
| d          |
+------------+
| 0000000001 |
| 0000000002 |
| 0000000003 |
| 0000000004 |
| 0000000005 |
| 0000000006 |
+------------+

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO t1 VALUES (-7);
ERROR 1264 (22003): Out of range value for column 'd' at row 1

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO t1 VALUES (-7);
Query OK, 1 row affected, 1 warning (0.02 sec)
Warning (Code 1264): Out of range value for column 'd' at row 1

SELECT * FROM t1;
+------------+
| d          |
+------------+
| 0000000001 |
| 0000000002 |
| 0000000003 |
| 0000000004 |
| 0000000005 |
| 0000000006 |
| 0000000000 |
+------------+

See Also

ENUM

Syntax

ENUM('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]

Description

An enumeration. A string object that can have only one value, chosen from the list of values 'value1', 'value2', ..., NULL or the special '' error value. In theory, an ENUM column can have a maximum of 65,535 distinct values; in practice, the real maximum depends on many factors. ENUM values are represented internally as integers.

Trailing spaces are automatically stripped from ENUM values on table creation.

ENUMs require relatively little storage space compared to strings, either one or two bytes depending on the number of enumeration values.

NULL and empty values

An ENUM can also contain NULL and empty values. If the ENUM column is declared to permit NULL values, NULL becomes a valid value, as well as the default value (see below). If strict SQL Mode is not enabled, and an invalid value is inserted into an ENUM, a special empty string, with an index value of zero (see Numeric index, below), is inserted, with a warning. This may be confusing, because the empty string is also a possible value, and the only difference if that is this case its index is not 0. Inserting will fail with an error if strict mode is active.

If a DEFAULT clause is missing, the default value will be:

  • NULL if the column is nullable;
  • otherwise, the first value in the enumeration.

Numeric index

ENUM values are indexed numerically in the order they are defined, and sorting will be performed in this numeric order. We suggest not using ENUM to store numerals, as there is little to no storage space benefit, and it is easy to confuse the enum integer with the enum numeral value by leaving out the quotes.

An ENUM defined as ENUM('apple','orange','pear') would have the following index values:

IndexValue
NULLNULL
0''
1'apple'
2'orange'
3'pear'

Examples

CREATE TABLE fruits (
  id INT NOT NULL auto_increment PRIMARY KEY,
  fruit ENUM('apple','orange','pear'),
  bushels INT);

DESCRIBE fruits;
+---------+-------------------------------+------+-----+---------+----------------+
| Field   | Type                          | Null | Key | Default | Extra          |
+---------+-------------------------------+------+-----+---------+----------------+
| id      | int(11)                       | NO   | PRI | NULL    | auto_increment |
| fruit   | enum('apple','orange','pear') | YES  |     | NULL    |                |
| bushels | int(11)                       | YES  |     | NULL    |                |
+---------+-------------------------------+------+-----+---------+----------------+

INSERT INTO fruits
    (fruit,bushels) VALUES
    ('pear',20),
    ('apple',100),
    ('orange',25);

INSERT INTO fruits
    (fruit,bushels) VALUES
    ('avocado',10);
ERROR 1265 (01000): Data truncated for column 'fruit' at row 1

SELECT * FROM fruits;
+----+--------+---------+
| id | fruit  | bushels |
+----+--------+---------+
|  1 | pear   |      20 |
|  2 | apple  |     100 |
|  3 | orange |      25 |
+----+--------+---------+

Selecting by numeric index:

SELECT * FROM fruits WHERE fruit=2;
+----+--------+---------+
| id | fruit  | bushels |
+----+--------+---------+
|  3 | orange |      25 |
+----+--------+---------+

Sorting is according to the index value:

CREATE TABLE enums (a ENUM('2','1'));

INSERT INTO enums VALUES ('1'),('2');

SELECT * FROM enums ORDER BY a ASC;
+------+
| a    |
+------+
| 2    |
| 1    |
+------+

It's easy to get confused between returning the enum integer with the stored value, so we don't suggest using ENUM to store numerals. The first example returns the 1st indexed field ('2' has an index value of 1, as it's defined first), while the second example returns the string value '1'.

SELECT * FROM enums WHERE a=1;
+------+
| a    |
+------+
| 2    |
+------+

SELECT * FROM enums WHERE a='1';
+------+
| a    |
+------+
| 1    |
+------+

See Also

ST_LineStringFromWKB

A synonym for ST_LineFromWKB.

ST_PointFromWKB

Syntax

ST_PointFromWKB(wkb[,srid])
PointFromWKB(wkb[,srid])

Description

Constructs a POINT value using its WKB representation and SRID.

ST_PointFromWKB() and PointFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(ST_PointFromText('POINT(0 4)'));

SELECT ST_AsText(ST_PointFromWKB(@g)) AS p;
+------------+
| p          |
+------------+
| POINT(0 4) |
+------------+

ST_PolyFromWKB

Syntax

ST_PolyFromWKB(wkb[,srid])
ST_PolygonFromWKB(wkb[,srid])
PolyFromWKB(wkb[,srid])
PolygonFromWKB(wkb[,srid])

Description

Constructs a POLYGON value using its WKB representation and SRID.

ST_PolyFromWKB(), ST_PolygonFromWKB(), PolyFromWKB() and PolygonFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(ST_PolyFromText('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))'));

SELECT ST_AsText(ST_PolyFromWKB(@g)) AS p;
+----------------------------------------+
| p                                      |
+----------------------------------------+
| POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) |
+----------------------------------------+

ST_PolygonFromWKB

A synonym for ST_PolyFromWKB.

DOUBLE

Syntax

DOUBLE[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
DOUBLE PRECISION[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
REAL[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]

Description

A normal-size (double-precision) floating-point number (see FLOAT for a single-precision floating-point number).

Allowable values are:

  • -1.7976931348623157E+308 to -2.2250738585072014E-308
  • 0
  • 2.2250738585072014E-308 to 1.7976931348623157E+308

These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system.

M is the total number of digits and D is the number of digits following the decimal point. If M and D are omitted, values are stored to the limits allowed by the hardware. A double-precision floating-point number is accurate to approximately 15 decimal places.

UNSIGNED, if specified, disallows negative values.

ZEROFILL, if specified, pads the number with zeros, up to the total number of digits specified by M.

REAL and DOUBLE PRECISION are synonyms, unless the REAL_AS_FLOAT SQL mode is enabled, in which case REAL is a synonym for FLOAT rather than DOUBLE.

See Floating Point Accuracy for issues when using floating-point numbers.

For more details on the attributes, see Numeric Data Type Overview.

Examples

CREATE TABLE t1 (d DOUBLE(5,0) zerofill);

INSERT INTO t1 VALUES (1),(2),(3),(4);

SELECT * FROM t1;
+-------+
| d     |
+-------+
| 00001 |
| 00002 |
| 00003 |
| 00004 |
+-------+

FLOAT

Syntax

FLOAT[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]

Contents

  1. Syntax
  2. Description

Description

A small (single-precision) floating-point number (see DOUBLE for a regular-size floating point number). Allowable values are:

  • -3.402823466E+38 to -1.175494351E-38
  • 0
  • 1.175494351E-38 to 3.402823466E+38.

These are the theoretical limits, based on the IEEE standard. The actual range might be slightly smaller depending on your hardware or operating system.

M is the total number of digits and D is the number of digits following the decimal point. If M and D are omitted, values are stored to the limits allowed by the hardware. A single-precision floating-point number is accurate to approximately 7 decimal places.

UNSIGNED, if specified, disallows negative values.

Using FLOAT might give you some unexpected problems because all calculations in MariaDB are done with double precision. See Floating Point Accuracy.

For more details on the attributes, see Numeric Data Type Overview.

JSON Data Type

MariaDB starting with 10.2.7

The JSON alias was added in MariaDB 10.2.7. This was done to make it possible to use JSON columns in statement based replication from MySQL to MariaDB and to make it possible for MariaDB to read mysqldumps from MySQL.

JSON is an alias for LONGTEXT introduced for compatibility reasons with MySQL's JSON data type. MariaDB implements this as a LONGTEXT rather, as the JSON data type contradicts the SQL standard, and MariaDB's benchmarks indicate that performance is at least equivalent.

In order to ensure that a a valid json document is inserted, the JSON_VALID function can be used as a CHECK constraint. This constraint is automatically included for types using the JSON alias from MariaDB 10.4.3.

Examples

CREATE TABLE t (j JSON);

DESC t;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| j     | longtext | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+

With validation:

CREATE TABLE t2 (
  j JSON 
  CHECK (JSON_VALID(j))
);

INSERT INTO t2 VALUES ('invalid');
ERROR 4025 (23000): CONSTRAINT `j` failed for `test`.`t2`

INSERT INTO t2 VALUES ('{"id": 1, "name": "Monty"}');
Query OK, 1 row affected (0.13 sec)

Replicating JSON Data Between MySQL and MariaDB

The JSON type in MySQL stores the JSON object in a compact form, not as LONGTEXT as in MariaDB. This means that row based replication will not work for JSON types from MySQL to MariaDB.

There are a a few different ways to solve this:

  • Use statement based replication.
  • Change the JSON column to type TEXT in MySQL
  • If you must use row-based replication and cannot change the MySQL master from JSON to TEXT, you can try to introduce an intermediate MySQL slave and change the column type from JSON to TEXT on it. Then you replicate from this intermediate slave to MariaDB.

Converting a MySQL TABLE with JSON Fields to MariaDB

MariaDB can't directly access MySQL's JSON format.

There are a a few different ways to move the table to MariaDB:

Differences Between MySQL JSON Strings and MariaDB JSON Strings

  • In MySQL, JSON is an object and is compared according to json values. In MariaDB JSON strings are normal strings and compared as strings. One exception is when using JSON_EXTRACT() in which case strings are unescaped before comparison.

See Also

BOUNDARY

A synonym for ST_BOUNDARY.

DIMENSION

A synonym for ST_DIMENSION.

ENVELOPE

A synonym for ST_ENVELOPE.

GeometryN

A synonym for ST_GeometryN.

GeometryType

A synonym for ST_GeometryType.

IsClosed

A synonym for ST_IsClosed.

IsEmpty

A synonym for ST_IsEmpty.

IsRing

A synonym for ST_IsRing.

IsSimple

A synonym for ST_IsSImple.

NumGeometries

A synonym for ST_NumGeometries.

SRID

A synonym for ST_SRID.

ST_DIMENSION

Syntax

ST_Dimension(g)
Dimension(g)

Description

Returns the inherent dimension of the geometry value g. The result can be

DimensionDefinition
-1empty geometry
0geometry with no length or area
1geometry with no area but nonzero length
2geometry with nonzero area

ST_Dimension() and Dimension() are synonyms.

Examples

SELECT Dimension(GeomFromText('LineString(1 1,2 2)'));
+------------------------------------------------+
| Dimension(GeomFromText('LineString(1 1,2 2)')) |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+

Geometry Types

Description

MariaDB provides a standard way of creating spatial columns for geometry types, for example, with CREATE TABLE or ALTER TABLE. Currently, spatial columns are supported for MyISAM, InnoDB, NDB, and ARCHIVE tables. See also SPATIAL INDEX.

The basic geometry type is GEOMETRY. But the type can be more specific. The following types are supported:

Examples

Note: For clarity, only one type is listed per table in the examples below, but a table row can contain multiple types. For example:

CREATE TABLE object (shapeA POLYGON, shapeB LINESTRING);

POINT

CREATE TABLE gis_point  (g POINT);
SHOW FIELDS FROM gis_point;
INSERT INTO gis_point VALUES
    (PointFromText('POINT(10 10)')),
    (PointFromText('POINT(20 10)')),
    (PointFromText('POINT(20 20)')),
    (PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));

LINESTRING

CREATE TABLE gis_line  (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
    (LineFromText('LINESTRING(0 0,0 10,10 0)')),
    (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')),
    (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10)))));

POLYGON

CREATE TABLE gis_polygon   (g POLYGON);
SHOW FIELDS FROM gis_polygon;
INSERT INTO gis_polygon VALUES
    (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0))))));

MULTIPOINT

CREATE TABLE gis_multi_point (g MULTIPOINT);
SHOW FIELDS FROM gis_multi_point;
INSERT INTO gis_multi_point VALUES
    (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')),
    (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
    (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10)))));

MULTILINESTRING

CREATE TABLE gis_multi_line (g MULTILINESTRING);
SHOW FIELDS FROM gis_multi_line;
INSERT INTO gis_multi_line VALUES
    (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')),
    (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
    (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21, 7))))));

MULTIPOLYGON

CREATE TABLE gis_multi_polygon  (g MULTIPOLYGON);
SHOW FIELDS FROM gis_multi_polygon;
INSERT INTO gis_multi_polygon VALUES
    (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));

GEOMETRYCOLLECTION

CREATE TABLE gis_geometrycollection  (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
    (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')),
    (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))),
    (GeomFromText('GeometryCollection()')),
    (GeomFromText('GeometryCollection EMPTY'));

GEOMETRY

CREATE TABLE gis_geometry (g GEOMETRY);
SHOW FIELDS FROM gis_geometry;
INSERT into gis_geometry SELECT * FROM gis_point;
INSERT into gis_geometry SELECT * FROM gis_line;
INSERT into gis_geometry SELECT * FROM gis_polygon;
INSERT into gis_geometry SELECT * FROM gis_multi_point;
INSERT into gis_geometry SELECT * FROM gis_multi_line;
INSERT into gis_geometry SELECT * FROM gis_multi_polygon;
INSERT into gis_geometry SELECT * FROM gis_geometrycollection;

LONGTEXT

Syntax

LONGTEXT [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A TEXT column with a maximum length of 4,294,967,295 or 4GB (232 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. The effective maximum length of LONGTEXT columns also depends on the configured maximum packet size in the client/server protocol and available memory. Each LONGTEXT value is stored using a four-byte length prefix that indicates the number of bytes in the value.

From MariaDB 10.2.7, JSON is an alias for LONGTEXT. See JSON Data Type for details.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, CLOB is a synonym for LONGTEXT.

See Also

MEDIUMINT

Syntax

MEDIUMINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]

Description

A medium-sized integer. The signed range is -8388608 to 8388607. The unsigned range is 0 to 16777215.

ZEROFILL pads the integer with zeroes and assumes UNSIGNED (even if UNSIGNED is not specified).

INT3 is a synonym for MEDIUMINT.

For details on the attributes, see Numeric Data Type Overview.

Examples

CREATE TABLE mediumints (a MEDIUMINT,b MEDIUMINT UNSIGNED,c MEDIUMINT ZEROFILL);

DESCRIBE mediumints;
+-------+--------------------------------+------+-----+---------+-------+
| Field | Type                           | Null | Key | Default | Extra |
+-------+--------------------------------+------+-----+---------+-------+
| a     | mediumint(9)                   | YES  |     | NULL    |       |
| b     | mediumint(8) unsigned          | YES  |     | NULL    |       |
| c     | mediumint(8) unsigned zerofill | YES  |     | NULL    |       |
+-------+--------------------------------+------+-----+---------+-------+

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO mediumints VALUES (-10,-10,-10);
ERROR 1264 (22003): Out of range value for column 'b' at row 1

INSERT INTO mediumints VALUES (-10,10,-10);
ERROR 1264 (22003): Out of range value for column 'c' at row 1

INSERT INTO mediumints VALUES (-10,10,10);

INSERT INTO mediumints VALUES (8388608,8388608,8388608);
ERROR 1264 (22003): Out of range value for column 'a' at row 1

INSERT INTO mediumints VALUES (8388607,8388608,8388608);

SELECT * FROM mediumints;
+---------+---------+----------+
| a       | b       | c        |
+---------+---------+----------+
|     -10 |      10 | 00000010 |
| 8388607 | 8388608 | 08388608 |
+---------+---------+----------+

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO mediumints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.05 sec)
Warning (Code 1264): Out of range value for column 'b' at row 1
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO mediumints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO mediumints VALUES (-10,10,10);

INSERT INTO mediumints VALUES (8388608,8388608,8388608);
Query OK, 1 row affected, 1 warning (0.05 sec)
Warning (Code 1264): Out of range value for column 'a' at row 1

INSERT INTO mediumints VALUES (8388607,8388608,8388608);

SELECT * FROM mediumints;
+---------+---------+----------+
| a       | b       | c        |
+---------+---------+----------+
|     -10 |       0 | 00000000 |
|     -10 |       0 | 00000000 |
|     -10 |      10 | 00000000 |
|     -10 |      10 | 00000010 |
| 8388607 | 8388608 | 08388608 |
| 8388607 | 8388608 | 08388608 |
+---------+---------+----------+

See Also

ST_GEOMETRYN

Syntax

ST_GeometryN(gc,N)
GeometryN(gc,N)

Description

Returns the N-th geometry in the GeometryCollection gc. Geometries are numbered beginning with 1.

ST_GeometryN() and GeometryN() are synonyms.

Example

SET @gc = 'GeometryCollection(Point(1 1),LineString(12 14, 9 11))';

SELECT AsText(GeometryN(GeomFromText(@gc),1));
+----------------------------------------+
| AsText(GeometryN(GeomFromText(@gc),1)) |
+----------------------------------------+
| POINT(1 1)                             |
+----------------------------------------+

Numeric Data Type Overview

There are a number of numeric data types:

See the specific articles for detailed information on each.

SIGNED, UNSIGNED and ZEROFILL

Most numeric types can be defined as SIGNED, UNSIGNED or ZEROFILL, for example:

TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]

If SIGNED, or no attribute, is specified, a portion of the numeric type will be reserved for the sign (plus or minus). For example, a TINYINT SIGNED can range from -128 to 127.

If UNSIGNED is specified, no portion of the numeric type is reserved for the sign, so for integer types range can be larger. For example, a TINYINT UNSIGNED can range from 0 to 255. Floating point and fixed-point types also can be UNSIGNED, but this only prevents negative values from being stored and doesn't alter the range.

If ZEROFILL is specified, the column will be set to UNSIGNED and the spaces used by default to pad the field are replaced with zeros. ZEROFILL is ignored in expressions or as part of a UNION. ZEROFILL is a non-standard MySQL and MariaDB enhancement.

Note that although the preferred syntax indicates that the attributes are exclusive, more than one attribute can be specified.

Until MariaDB 10.2.7 (MDEV-8659), any combination of the attributes could be used in any order, with duplicates. In this case:

  • the presence of ZEROFILL makes the column UNSIGNED ZEROFILL.
  • the presence of UNSIGNED makes the column UNSIGNED.

From MariaDB 10.2.8, only the following combinations are supported:

  • SIGNED
  • UNSIGNED
  • ZEROFILL
  • UNSIGNED ZEROFILL
  • ZEROFILL UNSIGNED

The latter two should be replaced with simply ZEROFILL, but are still accepted by the parser.

Examples

CREATE TABLE zf (
  i1 TINYINT SIGNED,
  i2 TINYINT UNSIGNED,
  i3 TINYINT ZEROFILL
);

INSERT INTO zf VALUES (2,2,2);

SELECT * FROM zf;
+------+------+------+
| i1   | i2   | i3   |
+------+------+------+
|    2 |    2 |  002 |
+------+------+------+

Range

When attempting to add a value that is out of the valid range for the numeric type, MariaDB will react depending on the strict SQL_MODE setting.

If strict_mode has been set (the default from MariaDB 10.2.4), MariaDB will return an error.

If strict_mode has not been set (the default until MariaDB 10.2.3), MariaDB will adjust the number to fit in the field, returning a warning.

Examples

With strict_mode set:

SHOW VARIABLES LIKE 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------+
| Variable_name | Value                                                                                     |
+---------------+-------------------------------------------------------------------------------------------+
| sql_mode      | STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+-------------------------------------------------------------------------------------------+

CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT UNSIGNED);

INSERT INTO ranges VALUES (257,257,257);
ERROR 1264 (22003): Out of range value for column 'i1' at row 1

SELECT * FROM ranges;
Empty set (0.10 sec)

With strict_mode unset:

SHOW VARIABLES LIKE 'sql_mode%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_mode      |       |
+---------------+-------+

CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT UNSIGNED);

INSERT INTO ranges VALUES (257,257,257);
Query OK, 1 row affected, 2 warnings (0.00 sec)

SHOW WARNINGS;
+---------+------+---------------------------------------------+
| Level   | Code | Message                                     |
+---------+------+---------------------------------------------+
| Warning | 1264 | Out of range value for column 'i1' at row 1 |
| Warning | 1264 | Out of range value for column 'i3' at row 1 |
+---------+------+---------------------------------------------+
2 rows in set (0.00 sec)

SELECT * FROM ranges;
+------+------+------+
| i1   | i2   | i3   |
+------+------+------+
|  127 |  257 |  255 |
+------+------+------+

Auto_increment

The AUTO_INCREMENT attribute can be used to generate a unique identity for new rows. For more details, see auto_increment.

SMALLINT

Syntax

SMALLINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]

Description

A small integer. The signed range is -32768 to 32767. The unsigned range is 0 to 65535.

If a column has been set to ZEROFILL, all values will be prepended by zeros so that the SMALLINT value contains a number of M digits.

Note: If the ZEROFILL attribute has been specified, the column will automatically become UNSIGNED.

INT2 is a synonym for SMALLINT.

For more details on the attributes, see Numeric Data Type Overview.

Examples

CREATE TABLE smallints (a SMALLINT,b SMALLINT UNSIGNED,c SMALLINT ZEROFILL);

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO smallints VALUES (-10,-10,-10);
ERROR 1264 (22003): Out of range value for column 'b' at row 1

INSERT INTO smallints VALUES (-10,10,-10);
ERROR 1264 (22003): Out of range value for column 'c' at row 1

INSERT INTO smallints VALUES (-10,10,10);

INSERT INTO smallints VALUES (32768,32768,32768);
ERROR 1264 (22003): Out of range value for column 'a' at row 1

INSERT INTO smallints VALUES (32767,32768,32768);

SELECT * FROM smallints;
+-------+-------+-------+
| a     | b     | c     |
+-------+-------+-------+
|   -10 |    10 | 00010 |
| 32767 | 32768 | 32768 |
+-------+-------+-------+

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO smallints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.09 sec)
Warning (Code 1264): Out of range value for column 'b' at row 1
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO smallints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO smallints VALUES (-10,10,10);

INSERT INTO smallints VALUES (32768,32768,32768);
Query OK, 1 row affected, 1 warning (0.04 sec)
Warning (Code 1264): Out of range value for column 'a' at row 1

INSERT INTO smallints VALUES (32767,32768,32768);

SELECT * FROM smallints;
+-------+-------+-------+
| a     | b     | c     |
+-------+-------+-------+
|   -10 |     0 | 00000 |
|   -10 |    10 | 00000 |
|   -10 |    10 | 00010 |
| 32767 | 32768 | 32768 |
| 32767 | 32768 | 32768 |
+-------+-------+-------+

See Also

ST_GEOMETRYTYPE

Syntax

ST_GeometryType(g)
GeometryType(g)

Description

Returns as a string the name of the geometry type of which the geometry instance g is a member. The name corresponds to one of the instantiable Geometry subclasses.

ST_GeometryType() and GeometryType() are synonyms.

Examples

SELECT GeometryType(GeomFromText('POINT(1 1)'));
+------------------------------------------+
| GeometryType(GeomFromText('POINT(1 1)')) |
+------------------------------------------+
| POINT                                    |
+------------------------------------------+

ST_ISEMPTY

Syntax

ST_IsEmpty(g)
IsEmpty(g)

Description

IsEmpty is a function defined by the OpenGIS specification, but is not fully implemented by MariaDB or MySQL.

Since MariaDB and MySQL do not support GIS EMPTY values such as POINT EMPTY, as implemented it simply returns 1 if the geometry value g is invalid, 0 if it is valid, and NULL if the argument is NULL.

ST_IsEmpty() and IsEmpty() are synonyms.

ST_IsRing

MariaDB starting with 10.1.2

The ST_IsRing function was introduced in MariaDB 10.1.2

Syntax

ST_IsRing(g)
IsRing(g)

Description

Returns true if a given LINESTRING is a ring, that is, both ST_IsClosed and ST_IsSimple. A simple curve does not pass through the same point more than once. However, see MDEV-7510.

St_IsRing() and IsRing() are synonyms.

String Literals

Strings are sequences of characters and are enclosed with quotes.

The syntax is:

[_charset_name]'string' [COLLATE collation_name]

For example:

'The MariaDB Foundation'
_utf8 'Foundation' COLLATE utf8_unicode_ci;

Strings can either be enclosed in single quotes or in double quotes (the same character must be used to both open and close the string).

The ANSI SQL-standard does not permit double quotes for enclosing strings, and although MariaDB does by default, if the MariaDB server has enabled the ANSI_QUOTES_SQL SQL_MODE, double quotes will be treated as being used for identifiers instead of strings.

Strings that are next to each other are automatically concatenated. For example:

'The ' 'MariaDB ' 'Foundation'

and

'The MariaDB Foundation'

are equivalent.

The \ (backslash character) is used to escape characters (unless the SQL_MODE hasn't been set to NO_BACKSLASH_ESCAPES). For example:

'MariaDB's new features'

is not a valid string because of the single quote in the middle of the string, which is treated as if it closes the string, but is actually meant as part of the string, an apostrophe. The backslash character helps in situations like this:

'MariaDB\'s new features'

is now a valid string, and if displayed, will appear without the backslash.

SELECT 'MariaDB\'s new features';
+------------------------+
| MariaDB's new features |
+------------------------+
| MariaDB's new features |
+------------------------+

Another way to escape the quoting character is repeating it twice:

SELECT 'I''m here', """Double""";
+----------+----------+
| I'm here | "Double" |
+----------+----------+
| I'm here | "Double" |
+----------+----------+

Escape Sequences

There are other escape sequences also. Here is a full list:

Escape sequenceCharacter
\0ASCII NUL (0x00).
\'Single quote (“'”).
\"Double quote (“"”).
\bBackspace.
\nNewline, or linefeed,.
\rCarriage return.
\tTab.
\ZASCII 26 (Control+Z). See note following the table.
\\Backslash (“\”).
\%“%” character. See note following the table.
\_A “_” character. See note following the table.

Escaping the % and _ characters can be necessary when using the LIKE operator, which treats them as special characters.

The ASCII 26 character (\Z) needs to be escaped when included in a batch file which needs to be executed in Windows. The reason is that ASCII 26, in Windows, is the end of file (EOF).

Backslash (\), if not used as an escape character, must always be escaped. When followed by a character that is not in the above table, backslashes will simply be ignored.

TEXT

Syntax

TEXT[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A TEXT column with a maximum length of 65,535 (216 - 1) characters. The effective maximum length is less if the value contains multi-byte characters. Each TEXT value is stored using a two-byte length prefix that indicates the number of bytes in the value. If you need a bigger storage, consider using MEDIUMTEXT instead.

An optional length M can be given for this type. If this is done, MariaDB creates the column as the smallest TEXT type large enough to hold values M characters long.

Before MariaDB 10.2, all MariaDB collations were of type PADSPACE, meaning that TEXT (as well as VARCHAR and CHAR values) are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces.

Before MariaDB 10.2.1, BLOB and TEXT columns could not be assigned a DEFAULT value. This restriction was lifted in MariaDB 10.2.1.

Examples

Trailing spaces:

CREATE TABLE strtest (d TEXT(10));
INSERT INTO strtest VALUES('Maria   ');

SELECT d='Maria',d='Maria   ' FROM strtest;
+-----------+--------------+
| d='Maria' | d='Maria   ' |
+-----------+--------------+
|         1 |            1 |
+-----------+--------------+

SELECT d LIKE 'Maria',d LIKE 'Maria   ' FROM strtest;
+----------------+-------------------+
| d LIKE 'Maria' | d LIKE 'Maria   ' |
+----------------+-------------------+
|              0 |                 1 |
+----------------+-------------------+

Indexing

TEXT columns can only be indexed over a specified length. This means that they cannot be used as the primary key of a table norm until MariaDB 10.4, can a unique index be created on them.

MariaDB starting with 10.4

Starting with MariaDB 10.4, a unique index can be created on a TEXT column.

Internally, this uses hash indexing to quickly check the values and if a hash collision is found, the actual stored values are compared in order to retain the uniqueness.

Difference between VARCHAR and TEXT

  • VARCHAR columns can be fully indexed. TEXT columns can only be indexed over a specified length.
  • Using TEXT or BLOB in a SELECT query that uses temporary tables for storing intermediate results will force the temporary table to be disk based (using the Aria storage engine instead of the memory storage engine, which is a bit slower. This is not that bad as the Aria storage engine caches the rows in memory. To get the benefit of this, one should ensure that the aria_pagecache_buffer_size variable is big enough to hold most of the row and index data for temporary tables.

For Storage Engine Developers

  • Internally the full length of the VARCHAR column is allocated inside each TABLE objects record[] structure. As there are three such buffers, each open table will allocate 3 times max-length-to-store-varchar bytes of memory.
  • TEXT and BLOB columns are stored with a pointer (4 or 8 bytes) + a 1-4 bytes length. The TEXT data is only stored once. This means that internally TEXT uses less memory for each open table but instead has the additional overhead that each TEXT object needs to be allocated and freed for each row access (with some caching in between).

See Also

ST_IsSimple

Syntax

ST_IsSimple(g)
IsSimple(g)

Description

Returns true if the given Geometry has no anomalous geometric points, false if it does, or NULL if given a NULL value.

ST_IsSimple() and IsSimple() are synonyms.

Examples

A POINT is always simple.

SET @g = 'Point(1 2)';

SELECT ST_ISSIMPLE(GEOMFROMTEXT(@g));
+-------------------------------+
| ST_ISSIMPLE(GEOMFROMTEXT(@g)) |
+-------------------------------+
|                             1 |
+-------------------------------+

ST_NUMGEOMETRIES

Syntax

ST_NumGeometries(gc)
NumGeometries(gc)

Description

Returns the number of geometries in the GeometryCollection gc.

ST_NumGeometries() and NumGeometries() are synonyms.

Example

SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))';

SELECT NUMGEOMETRIES(GeomFromText(@gc));
+----------------------------------+
| NUMGEOMETRIES(GeomFromText(@gc)) |
+----------------------------------+
|                                2 |
+----------------------------------+

ST_RELATE

MariaDB starting with 10.1.2

The ST_RELATE() function was introduced in MariaDB 10.1.2

Syntax

ST_Relate(g1, g2, i)

Description

Returns true if Geometry g1 is spatially related to Geometryg2 by testing for intersections between the interior, boundary and exterior of the two geometries as specified by the values in intersection matrix pattern i.

ST_SRID

Syntax

ST_SRID(g)
SRID(g)

Description

Returns an integer indicating the Spatial Reference System ID for the geometry value g.

In MariaDB, the SRID value is just an integer associated with the geometry value. All calculations are done assuming Euclidean (planar) geometry.

ST_SRID() and SRID() are synonyms.

Examples

SELECT SRID(GeomFromText('LineString(1 1,2 2)',101));
+-----------------------------------------------+
| SRID(GeomFromText('LineString(1 1,2 2)',101)) |
+-----------------------------------------------+
|                                           101 |
+-----------------------------------------------+

TIME

Syntax

TIME [(<microsecond precision>)]

Description

A time. The range is '-838:59:59.999999' to '838:59:59.999999'. Microsecond precision can be from 0-6; if not specified 0 is used. Microseconds have been available since MariaDB 5.3.

MariaDB displays TIME values in 'HH:MM:SS.ssssss' format, but allows assignment of times in looser formats, including 'D HH:MM:SS', 'HH:MM:SS', 'HH:MM', 'D HH:MM', 'D HH', 'SS', or 'HHMMSS', as well as permitting dropping of any leading zeros when a delimiter is provided, for example '3:9:10'. For details, see date and time literals.

MariaDB starting with 10.1.2

MariaDB 10.1.2 introduced the --mysql56-temporal-format option, on by default, which allows MariaDB to store TIMEs using the same low-level format MySQL 5.6 uses.

Internal Format

In MariaDB 10.1.2 a new temporal format was introduced from MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP columns operate at lower levels. These changes allow these temporal data types to have fractional parts and negative values. You can disable this feature using the mysql56_temporal_format system variable.

Tables that include TIMESTAMP values that were created on an older version of MariaDB or that were created while the mysql56_temporal_format system variable was disabled continue to store data using the older data type format.

In order to update table columns from the older format to the newer format, execute an ALTER TABLE... MODIFY COLUMN statement that changes the column to the *same* data type. This change may be needed if you want to export the table's tablespace and import it onto a server that has mysql56_temporal_format=ON set (see MDEV-15225).

For instance, if you have a TIME column in your table:

SHOW VARIABLES LIKE 'mysql56_temporal_format';

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON    |
+-------------------------+-------+

ALTER TABLE example_table MODIFY ts_col TIME;

When MariaDB executes the ALTER TABLE statement, it converts the data from the older temporal format to the newer one.

In the event that you have several tables and columns using temporal data types that you want to switch over to the new format, make sure the system variable is enabled, then perform a dump and restore using mysqldump. The columns using relevant temporal data types are restored using the new temporal format.

Starting from MariaDB 10.5.1 columns with old temporal formats are marked with a /* mariadb-5.3 */ comment in the output of SHOW CREATE TABLE, SHOW COLUMNS, DESCRIBE statements, as well as in the COLUMN_TYPE column of the INFORMATION_SCHEMA.COLUMNS Table.

SHOW CREATE TABLE mariadb5312_time\G
*************************** 1. row ***************************
       Table: mariadb5312_time
Create Table: CREATE TABLE `mariadb5312_time` (
  `t0` time /* mariadb-5.3 */ DEFAULT NULL,
  `t6` time(6) /* mariadb-5.3 */ DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Note, columns with the current format are not marked with a comment.

Examples

INSERT INTO time VALUES ('90:00:00'), ('800:00:00'), (800), (22), (151413), ('9:6:3'), ('12 09');

SELECT * FROM time;
+-----------+
| t         |
+-----------+
| 90:00:00  |
| 800:00:00 |
| 00:08:00  |
| 00:00:22  |
| 15:14:13  |
| 09:06:03  |
| 297:00:00 |
+-----------+

See also

TINYINT

Syntax

TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]

Description

A very small integer. The signed range is -128 to 127. The unsigned range is 0 to 255. For details on the attributes, see Numeric Data Type Overview.

INT1 is a synonym for TINYINT. BOOL and BOOLEAN are synonyms for TINYINT(1).

Examples

CREATE TABLE tinyints (a TINYINT,b TINYINT UNSIGNED,c TINYINT ZEROFILL);

With strict_mode set, the default from MariaDB 10.2.4:

INSERT INTO tinyints VALUES (-10,-10,-10);
ERROR 1264 (22003): Out of range value for column 'b' at row 1

INSERT INTO tinyints VALUES (-10,10,-10);
ERROR 1264 (22003): Out of range value for column 'c' at row 1

INSERT INTO tinyints VALUES (-10,10,10);

SELECT * FROM tinyints;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|  -10 |   10 |  010 |
+------+------+------+

INSERT INTO tinyints VALUES (128,128,128);
ERROR 1264 (22003): Out of range value for column 'a' at row 1

INSERT INTO tinyints VALUES (127,128,128);

SELECT * FROM tinyints;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|  -10 |   10 |  010 |
|  127 |  128 |  128 |
+------+------+------+

With strict_mode unset, the default until MariaDB 10.2.3:

INSERT INTO tinyints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.08 sec)
Warning (Code 1264): Out of range value for column 'b' at row 1
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO tinyints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.11 sec)
Warning (Code 1264): Out of range value for column 'c' at row 1

INSERT INTO tinyints VALUES (-10,10,10);

SELECT * FROM tinyints;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|  -10 |    0 |  000 |
|  -10 |   10 |  000 |
|  -10 |   10 |  010 |
+------+------+------+

INSERT INTO tinyints VALUES (128,128,128);
Query OK, 1 row affected, 1 warning (0.19 sec)
Warning (Code 1264): Out of range value for column 'a' at row 1

INSERT INTO tinyints VALUES (127,128,128);

SELECT * FROM tinyints;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|  -10 |    0 |  000 |
|  -10 |   10 |  000 |
|  -10 |   10 |  010 |
|  127 |  128 |  128 |
|  127 |  128 |  128 |
+------+------+------+

See Also

VARBINARY

Syntax

VARBINARY(M)

Description

The VARBINARY type is similar to the VARCHAR type, but stores binary byte strings rather than non-binary character strings. M represents the maximum column length in bytes.

It contains no character set, and comparison and sorting are based on the numeric value of the bytes.

If the maximum length is exceeded, and SQL strict mode is not enabled , the extra characters will be dropped with a warning. If strict mode is enabled, an error will occur.

Unlike BINARY values, VARBINARYs are not right-padded when inserting.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, RAW is a synonym for VARBINARY.

Examples

Inserting too many characters, first with strict mode off, then with it on:

CREATE TABLE varbins (a VARBINARY(10));

INSERT INTO varbins VALUES('12345678901');
Query OK, 1 row affected, 1 warning (0.04 sec)

SELECT * FROM varbins;
+------------+
| a          |
+------------+
| 1234567890 |
+------------+

SET sql_mode='STRICT_ALL_TABLES';

INSERT INTO varbins VALUES('12345678901');
ERROR 1406 (22001): Data too long for column 'a' at row 1

Sorting is performed with the byte value:

TRUNCATE varbins;

INSERT INTO varbins VALUES('A'),('B'),('a'),('b');

SELECT * FROM varbins ORDER BY a;
+------+
| a    |
+------+
| A    |
| B    |
| a    |
| b    |
+------+

Using CAST to sort as a CHAR instead:

SELECT * FROM varbins ORDER BY CAST(a AS CHAR);
+------+
| a    |
+------+
| a    |
| A    |
| b    |
| B    |
+------+

See Also

ASCII

Syntax

ASCII(str)

Description

Returns the numeric ASCII value of the leftmost character of the string argument. Returns 0 if the given string is empty and NULL if it is NULL.

ASCII() works for 8-bit characters.

Examples

SELECT ASCII(9);
+----------+
| ASCII(9) |
+----------+
|       57 |
+----------+

SELECT ASCII('9');
+------------+
| ASCII('9') |
+------------+
|         57 |
+------------+

SELECT ASCII('abc');
+--------------+
| ASCII('abc') |
+--------------+
|           97 |
+--------------+

BIN

Syntax

BIN(N)

Description

Returns a string representation of the binary value of the given longlong (that is, BIGINT) number. This is equivalent to CONV(N,10,2). The argument should be positive. If it is a FLOAT, it will be truncated. Returns NULL if the argument is NULL.

Examples

SELECT BIN(12);
+---------+
| BIN(12) |
+---------+
| 1100    |
+---------+

See Also

BIT_LENGTH

Syntax

BIT_LENGTH(str)

Description

Returns the length of the given string argument in bits. If the argument is not a string, it will be converted to string. If the argument is NULL, it returns NULL.

Examples

SELECT BIT_LENGTH('text');
+--------------------+
| BIT_LENGTH('text') |
+--------------------+
|                 32 |
+--------------------+
SELECT BIT_LENGTH('');
+----------------+
| BIT_LENGTH('') |
+----------------+
|              0 |
+----------------+

Compatibility

PostgreSQL and Sybase support BIT_LENGTH().

VARCHAR

Syntax

[NATIONAL] VARCHAR(M) [CHARACTER SET charset_name] [COLLATE collation_name]

Description

A variable-length string. M represents the maximum column length in characters. The range of M is 0 to 65,532. The effective maximum length of a VARCHAR is subject to the maximum row size and the character set used. For example, utf8 characters can require up to three bytes per character, so a VARCHAR column that uses the utf8 character set can be declared to be a maximum of 21,844 characters.

Note: For the ColumnStore engine, M represents the maximum column length in bytes.

MariaDB stores VARCHAR values as a one-byte or two-byte length prefix plus data. The length prefix indicates the number of bytes in the value. A VARCHAR column uses one length byte if values require no more than 255 bytes, two length bytes if values may require more than 255 bytes.

MariaDB follows the standard SQL specification, and does not remove trailing spaces from VARCHAR values.

VARCHAR(0) columns can contain 2 values: an empty string or NULL. Such columns cannot be part of an index. The CONNECT storage engine does not support VARCHAR(0).

VARCHAR is shorthand for CHARACTER VARYING. NATIONAL VARCHAR is the standard SQL way to define that a VARCHAR column should use some predefined character set. MariaDB uses utf8 as this predefined character set, as does MySQL 4.1 and up. NVARCHAR is shorthand for NATIONAL VARCHAR.

Before MariaDB 10.2, all MariaDB collations were of type PADSPACE, meaning that VARCHAR (as well as CHAR and TEXT values) are compared without regard for trailing spaces. This does not apply to the LIKE pattern-matching operator, which takes into account trailing spaces. From MariaDB 10.2, a number of NO PAD collations are available.

If a unique index consists of a column where trailing pad characters are stripped or ignored, inserts into that column where values differ only by the number of trailing pad characters will result in a duplicate-key error.

Examples

The following are equivalent:

VARCHAR(30) CHARACTER SET utf8
NATIONAL VARCHAR(30)
NVARCHAR(30)
NCHAR VARCHAR(30)
NATIONAL CHARACTER VARYING(30)
NATIONAL CHAR VARYING(30)

Trailing spaces:

CREATE TABLE strtest (v VARCHAR(10));
INSERT INTO strtest VALUES('Maria   ');

SELECT v='Maria',v='Maria   ' FROM strtest;
+-----------+--------------+
| v='Maria' | v='Maria   ' |
+-----------+--------------+
|         1 |            1 |
+-----------+--------------+

SELECT v LIKE 'Maria',v LIKE 'Maria   ' FROM strtest;
+----------------+-------------------+
| v LIKE 'Maria' | v LIKE 'Maria   ' |
+----------------+-------------------+
|              0 |                 1 |
+----------------+-------------------+

Truncation

  • Depending on whether or not strict sql mode is set, you will either get a warning or an error if you try to insert a string that is too long into a VARCHAR column. If the extra characters are spaces, the spaces that can't fit will be removed and you will always get a warning, regardless of the sql mode setting.

Difference Between VARCHAR and TEXT

  • VARCHAR columns can be fully indexed. TEXT columns can only be indexed over a specified length.
  • Using TEXT or BLOB in a SELECT query that uses temporary tables for storing intermediate results will force the temporary table to be disk based (using the Aria storage engine instead of the memory storage engine, which is a bit slower. This is not that bad as the Aria storage engine caches the rows in memory. To get the benefit of this, one should ensure that the aria_pagecache_buffer_size variable is big enough to hold most of the row and index data for temporary tables.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, VARCHAR2 is a synonym.

For Storage Engine Developers

  • Internally the full length of the VARCHAR column is allocated inside each TABLE objects record[] structure. As there are three such buffers, each open table will allocate 3 times max-length-to-store-varchar bytes of memory.
  • TEXT and BLOB columns are stored with a pointer (4 or 8 bytes) + a 1-4 bytes length. The TEXT data is only stored once. This means that internally TEXT uses less memory for each open table but instead has the additional overhead that each TEXT object needs to be allocated and freed for each row access (with some caching in between).

See Also

YEAR Data Type

Syntax

YEAR[(4)]

Description

A year in two-digit or four-digit format. The default is four-digit format. Note that the two-digit format has been deprecated since MariaDB 5.5.27.

In four-digit format, the allowable values are 1901 to 2155, and 0000. In two-digit format, the allowable values are 70 to 69, representing years from 1970 to 2069. MariaDB displays YEAR values in YYYY format, but allows you to assign values to YEAR columns using either strings or numbers.

Inserting numeric zero has a different result for YEAR(4) and YEAR(2). For YEAR(2), the value 00 reflects the year 2000. For YEAR(4), the value 0000 reflects the year zero. This only applies to numeric zero. String zero always reflects the year 2000.

Examples

Accepting a string or a number:

CREATE TABLE y(y YEAR);

INSERT INTO y VALUES (1990),('2012');

SELECT * FROM y;
+------+
| y    |
+------+
| 1990 |
| 2012 |
+------+

With strict_mode set, the default from MariaDB 10.2.4:

Out of range:

INSERT INTO y VALUES (1005),('3080');
ERROR 1264 (22003): Out of range value for column 'y' at row 1

INSERT INTO y VALUES ('2013-12-12');
ERROR 1265 (01000): Data truncated for column 'y' at row 1

SELECT * FROM y;
+------+
| y    |
+------+
| 1990 |
| 2012 |
+------+

With strict_mode unset, the default until MariaDB 10.2.3:

Out of range:

INSERT INTO y VALUES (1005),('3080');
Query OK, 2 rows affected, 2 warnings (0.05 sec)
Records: 2  Duplicates: 0  Warnings: 2

SHOW WARNINGS;
+---------+------+--------------------------------------------+
| Level   | Code | Message                                    |
+---------+------+--------------------------------------------+
| Warning | 1264 | Out of range value for column 'y' at row 1 |
| Warning | 1264 | Out of range value for column 'y' at row 2 |
+---------+------+--------------------------------------------+

SELECT * FROM y;
+------+
| y    |
+------+
| 1990 |
| 2012 |
| 0000 |
| 0000 |
+------+

Truncating:

INSERT INTO y VALUES ('2013-12-12');
Query OK, 1 row affected, 1 warning (0.05 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1265 | Data truncated for column 'y' at row 1 |
+---------+------+----------------------------------------+

SELECT * FROM y;
+------+
| y    |
+------+
| 1990 |
| 2012 |
| 0000 |
| 0000 |
| 2013 |
+------+

Difference between YEAR(2) and YEAR(4), and string and numeric zero:

CREATE TABLE y2(y YEAR(4), y2 YEAR(2));
Query OK, 0 rows affected, 1 warning (0.40 sec)

Note (Code 1287): 'YEAR(2)' is deprecated and will be removed in a future release. 
 Please use YEAR(4) instead

INSERT INTO y2 VALUES(0,0),('0','0');

SELECT YEAR(y),YEAR(y2) FROM y2;
+---------+----------+
| YEAR(y) | YEAR(y2) |
+---------+----------+
|       0 |     2000 |
|    2000 |     2000 |
+---------+----------+

See Also

CHARACTER_LENGTH

Syntax

CHARACTER_LENGTH(str)

Description

CHARACTER_LENGTH() is a synonym for CHAR_LENGTH().

INSTR

Syntax

INSTR(str,substr)

Description

Returns the position of the first occurrence of substring substr in string str. This is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed.

INSTR() performs a case-insensitive search.

If any argument is NULL, returns NULL.

Examples

SELECT INSTR('foobarbar', 'bar');
+---------------------------+
| INSTR('foobarbar', 'bar') |
+---------------------------+
|                         4 |
+---------------------------+

SELECT INSTR('My', 'Maria');
+----------------------+
| INSTR('My', 'Maria') |
+----------------------+
|                    0 |
+----------------------+

See Also

  • LOCATE() ; Returns the position of a string within a string
  • SUBSTRING_INDEX() ; Returns the substring from string before count occurrences of a delimiter

BEGIN END

Syntax

[begin_label:] BEGIN [NOT ATOMIC]
    [statement_list]
END [end_label]

NOT ATOMIC is required when used outside of a stored procedure. Inside stored procedures or within an anonymous block, BEGIN alone starts a new anonymous block.

Description

BEGIN ... END syntax is used for writing compound statements. A compound statement can contain multiple statements, enclosed by the BEGIN and END keywords. statement_list represents a list of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. statement_list is optional, which means that the empty compound statement (BEGIN END) is legal.

Note that END will perform a commit. If you are running in autocommit mode, every statement will be committed separately. If you are not running in autocommit mode, you must execute a COMMIT or ROLLBACK after END to get the database up to date.

Use of multiple statements requires that a client is able to send statement strings containing the ; statement delimiter. This is handled in the mysql command-line client with the DELIMITER command. Changing the ; end-of-statement delimiter (for example, to //) allows ; to be used in a program body.

A compound statement within a stored program can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

BEGIN ... END constructs can be nested. Each block can define its own variables, a CONDITION, a HANDLER and a CURSOR, which don't exist in the outer blocks. The most local declarations override the outer objects which use the same name (see example below).

The declarations order is the following:

Note that DECLARE HANDLER contains another BEGIN ... END construct.

Here is an example of a very simple, anonymous block:

BEGIN NOT ATOMIC
SET @a=1;
CREATE TABLE test.t1(a INT);
END|

Below is an example of nested blocks in a stored procedure:

CREATE PROCEDURE t( )
BEGIN
   DECLARE x TINYINT UNSIGNED DEFAULT 1;
   BEGIN
      DECLARE x CHAR(2) DEFAULT '02';
       DECLARE y TINYINT UNSIGNED DEFAULT 10;
       SELECT x, y;
   END;
   SELECT x;
END;

In this example, a TINYINT variable, x is declared in the outter block. But in the inner block x is re-declared as a CHAR and an y variable is declared. The inner SELECT shows the "new" value of x, and the value of y. But when x is selected in the outer block, the "old" value is returned. The final SELECT doesn't try to read y, because it doesn't exist in that context.

See Also

CASE Statement

Syntax

CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE

Or:

CASE
    WHEN search_condition THEN statement_list
    [WHEN search_condition THEN statement_list] ...
    [ELSE statement_list] 
END CASE

Description

The text on this page describes the CASE statement for stored programs. See the CASE OPERATOR for details on the CASE operator outside of stored programs.

The CASE statement for stored programs implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END. implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

If no when_value or search_condition matches the value tested and the CASE statement contains no ELSE clause, a Case not found for CASE statement error results.

Each statement_list consists of one or more statements; an empty statement_list is not allowed. To handle situations where no value is matched by any WHEN clause, use an ELSE containing an empty BEGIN ... END block, as shown in this example:

DELIMITER |
CREATE PROCEDURE p()
BEGIN
  DECLARE v INT DEFAULT 1;
  CASE v
    WHEN 2 THEN SELECT v;
    WHEN 3 THEN SELECT 0;
    ELSE BEGIN END;
  END CASE;
END;
|

The indentation used here in the ELSE clause is for purposes of clarity only, and is not otherwise significant. See Delimiters in the mysql client for more on the use of the delimiter command.

Note: The syntax of the CASE statement used inside stored programs differs slightly from that of the SQL CASE expression described in CASE OPERATOR. The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END.

DECLARE CONDITION

Syntax

DECLARE condition_name CONDITION FOR condition_value

condition_value:
    SQLSTATE [VALUE] sqlstate_value
  | mysql_error_code

Description

The DECLARE ... CONDITION statement defines a named error condition. It specifies a condition that needs specific handling and associates a name with that condition. Later, the name can be used in a DECLARE ... HANDLER, SIGNAL or RESIGNAL statement (as long as the statement is located in the same BEGIN ... END block).

Conditions must be declared after local variables, but before CURSORs and HANDLERs.

A condition_value for DECLARE ... CONDITION can be an SQLSTATE value (a 5-character string literal) or a MySQL error code (a number). You should not use SQLSTATE value '00000' or MySQL error code 0, because those indicate sucess rather than an error condition. If you try, or if you specify an invalid SQLSTATE value, an error like this is produced:

ERROR 1407 (42000): Bad SQLSTATE: '00000'

For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.

LCASE

Syntax

LCASE(str)

Description

LCASE() is a synonym for LOWER().

LEFT

Syntax

LEFT(str,len)

Description

Returns the leftmost len characters from the string str, or NULL if any argument is NULL.

Examples

SELECT LEFT('MariaDB', 5);
+--------------------+
| LEFT('MariaDB', 5) |
+--------------------+
| Maria              |
+--------------------+

LENGTHB

MariaDB starting with 10.3.1

Introduced in MariaDB 10.3.1 as part of the Oracle compatibility enhancements.

Syntax

LENGTHB(str)

Description

LENGTHB() returns the length of the given string, in bytes. When Oracle mode is not set, this is a synonym for LENGTH.

A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTHB() returns 10, whereas CHAR_LENGTH() returns 5.

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

MID

Syntax

MID(str,pos,len)

Description

MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len).

Examples

SELECT MID('abcd',4,1);
+-----------------+
| MID('abcd',4,1) |
+-----------------+
| d               |
+-----------------+

SELECT MID('abcd',2,2);
+-----------------+
| MID('abcd',2,2) |
+-----------------+
| bc              |
+-----------------+

A negative starting position:

SELECT MID('abcd',-2,4);
+------------------+
| MID('abcd',-2,4) |
+------------------+
| cd               |
+------------------+

NOT LIKE

Syntax

expr NOT LIKE pat [ESCAPE 'escape_char']

Description

This is the same as NOT (expr LIKE pat [ESCAPE 'escape_char']).

DECLARE HANDLER

Syntax

DECLARE handler_type HANDLER
    FOR condition_value [, condition_value] ...
    statement

handler_type:
    CONTINUE
  | EXIT 
  | UNDO

condition_value:
    SQLSTATE [VALUE] sqlstate_value
  | condition_name
  | SQLWARNING
  | NOT FOUND
  | SQLEXCEPTION
  | mariadb_error_code

Description

The DECLARE ... HANDLER statement specifies handlers that each may deal with one or more conditions. If one of these conditions occurs, the specified statement is executed. statement can be a simple statement (for example, SET var_name = value), or it can be a compound statement written using BEGIN and END.

Handlers must be declared after local variables, a CONDITION and a CURSOR.

For a CONTINUE handler, execution of the current program continues after execution of the handler statement. For an EXIT handler, execution terminates for the BEGIN ... END compound statement in which the handler is declared. (This is true even if the condition occurs in an inner block.) The UNDO handler type statement is not supported.

If a condition occurs for which no handler has been declared, the default action is EXIT.

A condition_value for DECLARE ... HANDLER can be any of the following values:

  • An SQLSTATE value (a 5-character string literal) or a MariaDB error code (a number). You should not use SQLSTATE value '00000' or MariaDB error code 0, because those indicate sucess rather than an error condition. For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.
  • A condition name previously specified with DECLARE ... CONDITION. It must be in the same stored program. See DECLARE CONDITION.
  • SQLWARNING is shorthand for the class of SQLSTATE values that begin with '01'.
  • NOT FOUND is shorthand for the class of SQLSTATE values that begin with '02'. This is relevant only the context of cursors and is used to control what happens when a cursor reaches the end of a data set. If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition). An example is shown in Cursor Overview. This condition also occurs for SELECT ... INTO var_list statements that retrieve no rows.
  • SQLEXCEPTION is shorthand for the class of SQLSTATE values that do not begin with '00', '01', or '02'.

When an error raises, in some cases it could be handled by multiple HANDLERs. For example, there may be an handler for 1050 error, a separate handler for the 42S01 SQLSTATE, and another separate handler for the SQLEXCEPTION class: in theory all occurrences of HANDLER may catch the 1050 error, but MariaDB chooses the HANDLER with the highest precedence. Here are the precedence rules:

  • Handlers which refer to an error code have the highest precedence.
  • Handlers which refer to a SQLSTATE come next.
  • Handlers which refer to an error class have the lowest precedence.

In some cases, a statement could produce multiple errors. If this happens, in some cases multiple handlers could have the highest precedence. In such cases, the choice of the handler is indeterminate.

Note that if an error occurs within a CONTINUE HANDLER block, it can be handled by another HANDLER. However, a HANDLER which is already in the stack (that is, it has been called to handle an error and its execution didn't finish yet) cannot handle new errorsthis prevents endless loops. For example, suppose that a stored procedure contains a CONTINUE HANDLER for SQLWARNING and another CONTINUE HANDLER for NOT FOUND. At some point, a NOT FOUND error occurs, and the execution enters the NOT FOUND HANDLER. But within that handler, a warning occurs, and the execution enters the SQLWARNING HANDLER. If another NOT FOUND error occurs, it cannot be handled again by the NOT FOUND HANDLER, because its execution is not finished.

When a DECLARE HANDLER block can handle more than one error condition, it may be useful to know which errors occurred. To do so, you can use the GET DIAGNOSTICS statement.

An error that is handled by a DECLARE HANDLER construct can be issued again using the RESIGNAL statement.

Below is an example using DECLARE HANDLER:

CREATE TABLE test.t (s1 INT, PRIMARY KEY (s1));

DELIMITER //

CREATE PROCEDURE handlerdemo ( )
     BEGIN
       DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2 = 1;
       SET @x = 1;
       INSERT INTO test.t VALUES (1);
       SET @x = 2;
       INSERT INTO test.t VALUES (1);
       SET @x = 3;
     END;
     //

DELIMITER ;

CALL handlerdemo( );

SELECT @x;
+------+
| @x   |
+------+
|    3 |
+------+

DECLARE Variable

Syntax

DECLARE var_name [, var_name] ... [[ROW] TYPE OF]] type [DEFAULT value]

Description

This statement is used to declare local variables within stored programs. To provide a default value for the variable, include a DEFAULT clause. The value can be specified as an expression (even subqueries are permitted); it need not be a constant. If the DEFAULT clause is missing, the initial value is NULL.

Local variables are treated like stored routine parameters with respect to data type and overflow checking. See CREATE PROCEDURE.

Local variables must be declared before CONDITIONs, CURSORs and HANDLERs.

Local variable names are not case sensitive.

The scope of a local variable is within the BEGIN ... END block where it is declared. The variable can be referred to in blocks nested within the declaring block, except those blocks that declare a variable with the same name.

TYPE OF / ROW TYPE OF

MariaDB starting with 10.3

TYPE OF and ROW TYPE OF anchored data types for stored routines were introduced in MariaDB 10.3.

Anchored data types allow a data type to be defined based on another object, such as a table row, rather than specifically set in the declaration. If the anchor object changes, so will the anchored data type. This can lead to routines being easier to maintain, so that if the data type in the table is changed, it will automatically be changed in the routine as well.

Variables declared with ROW TYPE OF will have the same features as implicit ROW variables. It is not possible to use ROW TYPE OF variables in a LIMIT clause.

The real data type of TYPE OF and ROW TYPE OF table_name will become known at the very beginning of the stored routine call. ALTER TABLE or DROP TABLE statements performed inside the current routine on the tables that appear in anchors won't affect the data type of the anchored variables, even if the variable is declared after an ALTER TABLE or DROP TABLE statement.

The real data type of a ROW TYPE OF cursor_name variable will become known when execution enters into the block where the variable is declared. Data type instantiation will happen only once. In a cursor ROW TYPE OF variable that is declared inside a loop, its data type will become known on the very first iteration and won't change on further loop iterations.

The tables referenced in TYPE OF and ROW TYPE OF declarations will be checked for existence at the beginning of the stored routine call. CREATE PROCEDURE or CREATE FUNCTION will not check the referenced tables for existence.

Examples

TYPE OF and ROW TYPE OF from MariaDB 10.3:

DECLARE tmp TYPE OF t1.a; -- Get the data type from the column {{a}} in the table {{t1}}

DECLARE rec1 ROW TYPE OF t1; -- Get the row data type from the table {{t1}}

DECLARE rec2 ROW TYPE OF cur1; -- Get the row data type from the cursor {{cur1}}

See Also

FOR

MariaDB starting with 10.3

FOR loops were introduced in MariaDB 10.3.

Syntax

Integer range FOR loop:

[begin_label:]
FOR var_name IN [ REVERSE ] lower_bound .. upper_bound
DO statement_list
END FOR [ end_label ]

Explicit cursor FOR loop

[begin_label:]
FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)]
DO statement_list
END FOR [ end_label ]

Explicit cursor FOR loop (Oracle mode)

[begin_label:]
FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)]
LOOP
  statement_list
END LOOP [ end_label ]

Implicit cursor FOR loop

[begin_label:]
FOR record_name IN ( select_statement )
DO statement_list
END FOR [ end_label ]

Description

FOR loops allow code to be executed a fixed number of times.

In an integer range FOR loop, MariaDB will compare the lower bound and upper bound values, and assign the lower bound value to a counter. If REVERSE is not specified, and the upper bound value is greater than or equal to the counter, the counter will be incremented and the statement will continue, after which the loop is entered again. If the upper bound value is greater than the counter, the loop will be exited.

If REVERSE is specified, the counter is decremented, and the upper bound value needs to be less than or equal for the loop to continue.

Examples

Intger range FOR loop:

CREATE TABLE t1 (a INT);

DELIMITER //

FOR i IN 1..3
DO
  INSERT INTO t1 VALUES (i);
END FOR;
//

DELIMITER ;

SELECT * FROM t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
+------+

REVERSE integer range FOR loop:

CREATE OR REPLACE TABLE t1 (a INT);

DELIMITER //
FOR i IN REVERSE 4..12
    DO
    INSERT INTO t1 VALUES (i);
END FOR;
//
Query OK, 9 rows affected (0.422 sec)


DELIMITER ;

SELECT * FROM t1;
+------+
| a    |
+------+
|   12 |
|   11 |
|   10 |
|    9 |
|    8 |
|    7 |
|    6 |
|    5 |
|    4 |
+------+

Explicit cursor in Oracle mode:

SET sql_mode=ORACLE;

CREATE OR REPLACE TABLE t1 (a INT, b VARCHAR(32));

INSERT INTO t1 VALUES (10,'b0');
INSERT INTO t1 VALUES (11,'b1');
INSERT INTO t1 VALUES (12,'b2');

DELIMITER //

CREATE OR REPLACE PROCEDURE p1(pa INT) AS 
  CURSOR cur(va INT) IS
    SELECT a, b FROM t1 WHERE a=va;
BEGIN
  FOR rec IN cur(pa)
  LOOP
    SELECT rec.a, rec.b;
  END LOOP;
END;
//

DELIMITER ;

CALL p1(10);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    10 | b0    |
+-------+-------+

CALL p1(11);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    11 | b1    |
+-------+-------+

CALL p1(12);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    12 | b2    |
+-------+-------+

CALL p1(13);
Query OK, 0 rows affected (0.000 sec)

See Also

Labels

Syntax

label: <construct>
[label]

Labels are MariaDB identifiers which can be used to identify a BEGIN ... END construct or a loop. They have a maximum length of 16 characters and can be quoted with backticks (i.e.., `).

Labels have a start part and an end part. The start part must precede the portion of code it refers to, must be followed by a colon (:) and can be on the same or different line. The end part is optional and adds nothing, but can make the code more readable. If used, the end part must precede the construct's delimiter (;). Constructs identified by a label can be nested. Each construct can be identified by only one label.

Labels need not be unique in the stored program they belong to. However, a label for an inner loop cannot be identical to a label for an outer loop. In this case, the following error would be produced:

ERROR 1309 (42000): Redefining label <label_name>

LEAVE and ITERATE statements can be used to exit or repeat a portion of code identified by a label. They must be in the same Stored Routine, Trigger or Event which contains the target label.

Below is an example using a simple label that is used to exit a LOOP:

CREATE PROCEDURE `test_sp`()
BEGIN
   `my_label`:
   LOOP
      SELECT 'looping';
      LEAVE `my_label`;
   END LOOP;
   SELECT 'out of loop';
END;

The following label is used to exit a procedure, and has an end part:

CREATE PROCEDURE `test_sp`()
`my_label`:
BEGIN
   IF @var = 1 THEN
      LEAVE `my_label`;
   END IF;
   DO something();
END `my_label`;

LEAVE

Syntax

LEAVE label

This statement is used to exit the flow control construct that has the given label. The label must be in the same stored program, not in a caller procedure. LEAVE can be used within BEGIN ... END or loop constructs (LOOP, REPEAT, WHILE). In Stored Procedures, Triggers and Events, LEAVE can refer to the outmost BEGIN ... END construct; in that case, the program exits the procedure. In Stored Functions, RETURN can be used instead.

Note that LEAVE cannot be used to exit a DECLARE HANDLER block.

If you try to LEAVE a non-existing label, or if you try to LEAVE a HANDLER block, the following error will be produced:

ERROR 1308 (42000): LEAVE with no matching label: <label_name>

The following example uses LEAVE to exit the procedure if a condition is true:

CREATE PROCEDURE proc(IN p TINYINT)
CONTAINS SQL
`whole_proc`:
BEGIN
   SELECT 1;
   IF p < 1 THEN
      LEAVE `whole_proc`;
   END IF;
   SELECT 2;
END;

CALL proc(0);
+---+
| 1 |
+---+
| 1 |
+---+

See Also

NOT REGEXP

Syntax

expr NOT REGEXP pat, expr NOT RLIKE pat

Description

This is the same as NOT (expr REGEXP pat).

OCTET_LENGTH

Syntax

OCTET_LENGTH(str)

Description

OCTET_LENGTH() returns the length of the given string, in octets (bytes). This is a synonym for LENGTHB(), and, when Oracle mode from MariaDB 10.3 is not set, a synonym for LENGTH().

A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, OCTET_LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

ORD

Syntax

ORD(str)

Description

If the leftmost character of the string str is a multi-byte character, returns the code for that character, calculated from the numeric values of its constituent bytes using this formula:

  (1st byte code)
+ (2nd byte code x 256)
+ (3rd byte code x 256 x 256) ...

If the leftmost character is not a multi-byte character, ORD() returns the same value as the ASCII() function.

Examples

SELECT ORD('2');
+----------+
| ORD('2') |
+----------+
|       50 |
+----------+

See Also

  • ASCII() - Return ASCII value of first character
  • CHAR() - Create a character from an integer value

POSITION

Syntax

POSITION(substr IN str)

Description

POSITION(substr IN str) is a synonym for LOCATE(substr,str).

It's part of ODBC 3.0.

QUOTE

Syntax

QUOTE(str)

Description

Quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotes and with each instance of single quote ("'"), backslash ("\"), ASCII NUL, and Control-Z preceded by a backslash. If the argument is NULL, the return value is the word "NULL" without enclosing single quotes.

Examples

SELECT QUOTE("Don't!");
+-----------------+
| QUOTE("Don't!") |
+-----------------+
| 'Don\'t!'       |
+-----------------+

SELECT QUOTE(NULL); 
+-------------+
| QUOTE(NULL) |
+-------------+
| NULL        |
+-------------+

REPEAT LOOP

Syntax

[begin_label:] REPEAT
    statement_list
UNTIL search_condition
END REPEAT [end_label]

The statement list within a REPEAT statement is repeated until the search_condition is true. Thus, a REPEAT always enters the loop at least once. statement_list consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter.

A REPEAT statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

See Delimiters in the mysql client for more on client delimiter usage.

DELIMITER //

CREATE PROCEDURE dorepeat(p1 INT)
  BEGIN
    SET @x = 0;
    REPEAT SET @x = @x + 1; UNTIL @x > p1 END REPEAT;
  END
//

CALL dorepeat(1000)//

SELECT @x//
+------+
| @x   |
+------+
| 1001 |
+------+

RESIGNAL

Syntax

RESIGNAL [error_condition]
    [SET error_property
    [, error_property] ...]

error_condition:
    SQLSTATE [VALUE] 'sqlstate_value'
  | condition_name

error_property:
    error_property_name = <error_property_value>

error_property_name:
    CLASS_ORIGIN
  | SUBCLASS_ORIGIN
  | MESSAGE_TEXT
  | MYSQL_ERRNO
  | CONSTRAINT_CATALOG
  | CONSTRAINT_SCHEMA
  | CONSTRAINT_NAME
  | CATALOG_NAME
  | SCHEMA_NAME
  | TABLE_NAME
  | COLUMN_NAME
  | CURSOR_NAME

Description

The syntax of RESIGNAL and its semantics are very similar to SIGNAL. This statement can only be used within an error HANDLER. It produces an error, like SIGNAL. RESIGNAL clauses are the same as SIGNAL, except that they all are optional, even SQLSTATE. All the properties which are not specified in RESIGNAL, will be identical to the properties of the error that was received by the error HANDLER. For a description of the clauses, see diagnostics area.

Note that RESIGNAL does not empty the diagnostics area: it just appends another error condition.

RESIGNAL, without any clauses, produces an error which is identical to the error that was received by HANDLER.

If used out of a HANDLER construct, RESIGNAL produces the following error:

ERROR 1645 (0K000): RESIGNAL when handler not active

In MariaDB 5.5, if a HANDLER contained a CALL to another procedure, that procedure could use RESIGNAL. Since MariaDB 10.0, trying to do this raises the above error.

For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.

The following procedure tries to query two tables which don't exist, producing a 1146 error in both cases. Those errors will trigger the HANDLER. The first time the error will be ignored and the client will not receive it, but the second time, the error is re-signaled, so the client will receive it.

CREATE PROCEDURE test_error( )
BEGIN
   DECLARE CONTINUE HANDLER
      FOR 1146
   BEGIN
   IF @hide_errors IS FALSE THEN
      RESIGNAL;
   END IF;
   END;
   SET @hide_errors = TRUE;
   SELECT 'Next error will be ignored' AS msg;
   SELECT `c` FROM `temptab_one`;
   SELECT 'Next error won''t be ignored' AS msg;
   SET @hide_errors = FALSE;
   SELECT `c` FROM `temptab_two`;
END;

CALL test_error( );

+----------------------------+
| msg                        |
+----------------------------+
| Next error will be ignored |
+----------------------------+

+-----------------------------+
| msg                         |
+-----------------------------+
| Next error won't be ignored |
+-----------------------------+

ERROR 1146 (42S02): Table 'test.temptab_two' doesn't exist

The following procedure re-signals an error, modifying only the error message to clarify the cause of the problem.

CREATE PROCEDURE test_error()
BEGIN
   DECLARE CONTINUE HANDLER
   FOR 1146
   BEGIN
      RESIGNAL SET
      MESSAGE_TEXT = '`temptab` does not exist';
   END;
   SELECT `c` FROM `temptab`;
END;

CALL test_error( );
ERROR 1146 (42S02): `temptab` does not exist

As explained above, this works on MariaDB 5.5, but produces a 1645 error since 10.0.

CREATE PROCEDURE handle_error()
BEGIN
  RESIGNAL;
END;
CREATE PROCEDURE p()
BEGIN
  DECLARE EXIT HANDLER FOR SQLEXCEPTION CALL p();
  SIGNAL SQLSTATE '45000';
END;

See Also

SELECT INTO

Syntax

SELECT col_name [, col_name] ...
    INTO var_name [, var_name] ...
    table_expr

Description

SELECT ... INTO enables selected columns to be stored directly into variables. No resultset is produced. The query should return a single row. If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged. If the query returns multiple rows, error 1172 occurs (Result consisted of more than one row). If it is possible that the statement may retrieve multiple rows, you can use LIMIT 1 to limit the result set to a single row.

The INTO clause can also be specified at the end of the statement.

In the context of such statements that occur as part of events executed by the Event Scheduler, diagnostics messages (not only errors, but also warnings) are written to the error log, and, on Windows, to the application event log.

This statement can be used with both local variables and user-defined variables.

For the complete syntax, see SELECT.

Another way to set a variable's value is the SET statement.

SELECT ... INTO results are not stored in the query cache even if SQL_CACHE is specified.

Examples

SELECT id, data INTO @x,@y 
FROM test.t1 LIMIT 1;

See Also

REPEAT Function

Syntax

REPEAT(str,count)

Description

Returns a string consisting of the string str repeated count times. If count is less than 1, returns an empty string. Returns NULL if str or count are NULL.

Examples

SELECT QUOTE(REPEAT('MariaDB ',4));
+------------------------------------+
| QUOTE(REPEAT('MariaDB ',4))        |
+------------------------------------+
| 'MariaDB MariaDB MariaDB MariaDB ' |
+------------------------------------+

REPLACE Function

Syntax

REPLACE(str,from_str,to_str)

Description

Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.

Examples

SELECT REPLACE('www.mariadb.org', 'w', 'Ww');
+---------------------------------------+
| REPLACE('www.mariadb.org', 'w', 'Ww') |
+---------------------------------------+
| WwWwWw.mariadb.org                    |
+---------------------------------------+

REVERSE

Syntax

REVERSE(str)

Description

Returns the string str with the order of the characters reversed.

Examples

SELECT REVERSE('desserts');
+---------------------+
| REVERSE('desserts') |
+---------------------+
| stressed            |
+---------------------+

RIGHT

Syntax

RIGHT(str,len)

Description

Returns the rightmost len characters from the string str, or NULL if any argument is NULL.

Examples

SELECT RIGHT('MariaDB', 2);
+---------------------+
| RIGHT('MariaDB', 2) |
+---------------------+
| DB                  |
+---------------------+

SIGNAL

Syntax

SIGNAL error_condition
    [SET error_property
    [, error_property] ...]

error_condition:
    SQLSTATE [VALUE] 'sqlstate_value'
  | condition_name

error_property:
    error_property_name = <error_property_value>

error_property_name:
    CLASS_ORIGIN
  | SUBCLASS_ORIGIN
  | MESSAGE_TEXT
  | MYSQL_ERRNO
  | CONSTRAINT_CATALOG
  | CONSTRAINT_SCHEMA
  | CONSTRAINT_NAME
  | CATALOG_NAME
  | SCHEMA_NAME
  | TABLE_NAME
  | COLUMN_NAME
  | CURSOR_NAME

SIGNAL empties the diagnostics area and produces a custom error. This statement can be used anywhere, but is generally useful when used inside a stored program. When the error is produced, it can be caught by a HANDLER. If not, the current stored program, or the current statement, will terminate with the specified error.

Sometimes an error HANDLER just needs to SIGNAL the same error it received, optionally with some changes. Usually the RESIGNAL statement is the most convenient way to do this.

error_condition can be an SQLSTATE value or a named error condition defined via DECLARE CONDITION. SQLSTATE must be a constant string consisting of five characters. These codes are standard to ODBC and ANSI SQL. For customized errors, the recommended SQLSTATE is '45000'. For a list of SQLSTATE values used by MariaDB, see the MariaDB Error Codes page. The SQLSTATE can be read via the API method mysql_sqlstate( ).

To specify error properties user-defined variables and local variables can be used, as well as character set conversions (but you can't set a collation).

The error properties, their type and their default values are explained in the diagnostics area page.

Errors

If the SQLSTATE is not valid, the following error like this will be produced:

ERROR 1407 (42000): Bad SQLSTATE: '123456'

If a property is specified more than once, an error like this will be produced:

ERROR 1641 (42000): Duplicate condition information item 'MESSAGE_TEXT'

If you specify a condition name which is not declared, an error like this will be produced:

ERROR 1319 (42000): Undefined CONDITION: cond_name

If MYSQL_ERRNO is out of range, you will get an error like this:

ERROR 1231 (42000): Variable 'MYSQL_ERRNO' can't be set to the value of '0'

Examples

Here's what happens if SIGNAL is used in the client to generate errors:

SIGNAL SQLSTATE '01000';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;

+---------+------+------------------------------------------+
| Level   | Code | Message                                  |
+---------+------+------------------------------------------+
| Warning | 1642 | Unhandled user-defined warning condition |
+---------+------+------------------------------------------+
1 row in set (0.06 sec)

SIGNAL SQLSTATE '02000';
ERROR 1643 (02000): Unhandled user-defined not found condition

How to specify MYSQL_ERRNO and MESSAGE_TEXT properties:

SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO=30001, MESSAGE_TEXT='H
ello, world!';

ERROR 30001 (45000): Hello, world!

The following code shows how to use user variables, local variables and character set conversion with SIGNAL:

CREATE PROCEDURE test_error(x INT)
BEGIN
   DECLARE errno SMALLINT UNSIGNED DEFAULT 31001;
   SET @errmsg = 'Hello, world!';
   IF x = 1 THEN
      SIGNAL SQLSTATE '45000' SET
      MYSQL_ERRNO = errno,
      MESSAGE_TEXT = @errmsg;
   ELSE
      SIGNAL SQLSTATE '45000' SET
      MYSQL_ERRNO = errno,
      MESSAGE_TEXT = _utf8'Hello, world!';
   END IF;
END;

How to use named error conditions:

CREATE PROCEDURE test_error(n INT)
BEGIN
   DECLARE `too_big` CONDITION FOR SQLSTATE '45000';
   IF n > 10 THEN
      SIGNAL `too_big`;
   END IF;
END;

In this example, we'll define a HANDLER for an error code. When the error occurs, we SIGNAL a more informative error which makes sense for our procedure:

CREATE PROCEDURE test_error()
BEGIN
   DECLARE EXIT HANDLER
   FOR 1146
   BEGIN
      SIGNAL SQLSTATE '45000' SET
      MESSAGE_TEXT = 'Temporary tables not found; did you call init() procedure?';
   END;
   -- this will produce a 1146 error
   SELECT `c` FROM `temptab`;
END;

See Also

LINESTRING

Syntax

LineString(pt1,pt2,...)

Description

Constructs a WKB LineString value from a number of WKB Point arguments. If any argument is not a WKB Point, the return value is NULL. If the number of Point arguments is less than two, the return value is NULL.

Examples

SET @ls = 'LineString(1 1,2 2,3 3)';

SELECT AsText(EndPoint(GeomFromText(@ls)));
+-------------------------------------+
| AsText(EndPoint(GeomFromText(@ls))) |
+-------------------------------------+
| POINT(3 3)                          |
+-------------------------------------+

CREATE TABLE gis_line  (g LINESTRING);
INSERT INTO gis_line VALUES
    (LineFromText('LINESTRING(0 0,0 10,10 0)')),
    (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')),
    (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10)))));

SOUNDS LIKE

Syntax

expr1 SOUNDS LIKE expr2

Description

This is the same as SOUNDEX(expr1) = SOUNDEX(expr2).

Example

SELECT givenname, surname FROM users WHERE givenname SOUNDS LIKE "robert";
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto   | Castro  |
+-----------+---------+

SPACE

Syntax

SPACE(N)

Description

Returns a string consisting of N space characters. If N is NULL, returns NULL.

Examples

SELECT QUOTE(SPACE(6));
+-----------------+
| QUOTE(SPACE(6)) |
+-----------------+
| '      '        |
+-----------------+

STRCMP

Syntax

STRCMP(expr1,expr2)

Description

STRCMP() returns 0 if the strings are the same, -1 if the first argument is smaller than the second according to the current sort order, and 1 if the strings are otherwise not the same. Returns NULL is either argument is NULL.

Examples

SELECT STRCMP('text', 'text2');
+-------------------------+
| STRCMP('text', 'text2') |
+-------------------------+
|                      -1 |
+-------------------------+

SELECT STRCMP('text2', 'text');
+-------------------------+
| STRCMP('text2', 'text') |
+-------------------------+
|                       1 |
+-------------------------+

SELECT STRCMP('text', 'text');
+------------------------+
| STRCMP('text', 'text') |
+------------------------+
|                      0 |
+------------------------+

SUBSTR

Description

SUBSTR() is a synonym for SUBSTRING().

UCASE

Syntax

UCASE(str)

Description

UCASE() is a synonym for UPPER().

UPPER

Syntax

UPPER(str)

Description

Returns the string str with all characters changed to uppercase according to the current character set mapping. The default is latin1 (cp1252 West European).

SELECT UPPER(surname), givenname FROM users ORDER BY surname;
+----------------+------------+
| UPPER(surname) | givenname  |
+----------------+------------+
| ABEL           | Jacinto    |
| CASTRO         | Robert     |
| COSTA          | Phestos    |
| MOSCHELLA      | Hippolytos |
+----------------+------------+

UPPER() is ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). The description of LOWER() shows how to perform lettercase conversion of binary strings.

MULTIPOLYGON

Syntax

MultiPolygon(poly1,poly2,...)

Description

Constructs a WKB MultiPolygon value from a set of WKB Polygon arguments. If any argument is not a WKB Polygon, the return value is NULL.

Example

CREATE TABLE gis_multi_polygon  (g MULTIPOLYGON);
INSERT INTO gis_multi_polygon VALUES
    (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));

POLYGON

Syntax

Polygon(ls1,ls2,...)

Description

Constructs a WKB Polygon value from a number of WKB LineString arguments. If any argument does not represent the WKB of a LinearRing (that is, not a closed and simple LineString) the return value is NULL.

Note that according to the OpenGIS standard, a POLYGON should have exactly one ExteriorRing and all other rings should lie within that ExteriorRing and thus be the InteriorRings. Practically, however, some systems, including MariaDB's, permit polygons to have several 'ExteriorRings'. In the case of there being multiple, non-overlapping exterior rings ST_NUMINTERIORRINGS() will return 1.

Examples

SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))');

CREATE TABLE gis_polygon   (g POLYGON);
INSERT INTO gis_polygon VALUES
    (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0))))));

Non-overlapping 'polygon':

SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10 0,10 10,0 10,0 0),
  (-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings;
+------------------+
| NumInteriorRings |
+------------------+
|                1 |
+------------------+

ST_BUFFER

Syntax

ST_BUFFER(g1,r)
BUFFER(g1,r)

Description

Returns a geometry that represents all points whose distance from geometry g1 is less than or equal to distance, or radius, r.

Uses for this function could include creating for example a new geometry representing a buffer zone around an island.

BUFFER() is a synonym.

Examples

Determining whether a point is within a buffer zone:

SET @g1 = ST_GEOMFROMTEXT('POLYGON((10 10, 10 20, 20 20, 20 10, 10 10))');

SET @g2 = ST_GEOMFROMTEXT('POINT(8 8)');

SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,5));
+---------------------------------+
| ST_WITHIN(@g2,ST_BUFFER(@g1,5)) |
+---------------------------------+
|                               1 |
+---------------------------------+

SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,1));
+---------------------------------+
| ST_WITHIN(@g2,ST_BUFFER(@g1,1)) |
+---------------------------------+
|                               0 |
+---------------------------------+

ST_CONVEXHULL

MariaDB starting with 10.1.2

ST_ConvexHull() was introduced in MariaDB 10.1.2

Syntax

ST_ConvexHull(g)
ConvexHull(g)

Description

Given a geometry, returns a geometry that is the minimum convex geometry enclosing all geometries within the set. Returns NULL if the geometry value is NULL or an empty value.

ST_ConvexHull() and ConvexHull() are synonyms.

Examples

The ConvexHull of a single point is simply the single point:

SET @g = ST_GEOMFROMTEXT('Point(0 0)');

SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g)) |
+------------------------------+
| POINT(0 0)                   |
+------------------------------+
SET @g = ST_GEOMFROMTEXT('MultiPoint(0 0, 1 2, 2 3)');

SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g)) |
+------------------------------+
| POLYGON((0 0,1 2,2 3,0 0))   |
+------------------------------+
SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )');

SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+----------------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g))           |
+----------------------------------------+
| POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) |
+----------------------------------------+

ST_SYMDIFFERENCE

Syntax

ST_SYMDIFFERENCE(g1,g2)

Description

Returns a geometry that represents the portions of geometry g1 and geometry g2 that don't intersect.

Examples

SET @g1 = ST_GEOMFROMTEXT('LINESTRING(10 20, 10 40)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(10 15, 10 25)');

SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2));
+----------------------------------------------+
| ASTEXT(ST_SYMDIFFERENCE(@g1,@g2))            |
+----------------------------------------------+
| MULTILINESTRING((10 15,10 20),(10 25,10 40)) |
+----------------------------------------------+

SET @g2 = ST_GeomFromText('LINESTRING(10 20, 10 41)');

SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2));
+-----------------------------------+
| ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)) |
+-----------------------------------+
| LINESTRING(10 40,10 41)           |
+-----------------------------------+

CREATE FUNCTION

Syntax

CREATE [OR REPLACE] [DEFINER = {user | CURRENT_USER | role | CURRENT_ROLE }] [AGGREGATE] FUNCTION [IF NOT EXISTS] func_name ([func_parameter[,...]]) RETURNS type [characteristic ...] RETURN func_body

func_parameter: [ IN | OUT | INOUT | IN OUT ] param_name type

type: Any valid MariaDB data type

characteristic: LANGUAGE SQL | [NOT] DETERMINISTIC | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string'

func_body: Valid SQL procedure statement

Description

Use the CREATE FUNCTION statement to create a new stored function. You must have the CREATE ROUTINE database privilege to use CREATE FUNCTION. A function takes any number of arguments and returns a value from the function body. The function body can be any valid SQL expression as you would use, for example, in any select expression. If you have the appropriate privileges, you can call the function exactly as you would any built-in function. See Security below for details on privileges.

You can also use a variant of the CREATE FUNCTION statement to install a user-defined function (UDF) defined by a plugin. See CREATE FUNCTION (UDF) for details.

You can use a SELECT statement for the function body by enclosing it in parentheses, exactly as you would to use a subselect for any other expression. The SELECT statement must return a single value. If more than one column is returned when the function is called, error 1241 results. If more than one row is returned when the function is called, error 1242 results. Use a LIMIT clause to ensure only one row is returned.

You can also replace the RETURN clause with a BEGIN...END compound statement. The compound statement must contain a RETURN statement. When the function is called, the RETURN statement immediately returns its result, and any statements after RETURN are effectively ignored.

By default, a function is associated with the current database. To associate the function explicitly with a given database, specify the fully-qualified name as db_name.func_name when you create it. If the function name is the same as the name of a built-in function, you must use the fully qualified name when you call it.

The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive.

Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used.

For valid identifiers to use as function names, see Identifier Names.

IN | OUT | INOUT | IN OUT

MariaDB starting with 10.8.0

The function parameter qualifiers for IN, OUT, INOUT, and IN OUT were added in a 10.8.0 preview release. Prior to 10.8.0 quantifiers were supported only in procedures.

OUT, INOUT and its equivalent IN OUT, are only valid if called from SET and not SELECT. These quantifiers are especially useful for creating functions with more than one return value. This allows functions to be more complex and nested.

DELIMITER $$
CREATE FUNCTION add_func3(IN a INT, IN b INT, OUT c INT) RETURNS INT
BEGIN
  SET c = 100;
  RETURN a + b;
END;
$$
DELIMITER ;
 
SET @a = 2;
SET @b = 3;
SET @c = 0;
SET @res= add_func3(@a, @b, @c);

SELECT add_func3(@a, @b, @c);
ERROR 4186 (HY000): OUT or INOUT argument 3 for function add_func3 is not allowed here

DELIMITER $$
CREATE FUNCTION add_func4(IN a INT, IN b INT, d INT) RETURNS INT
BEGIN
  DECLARE c, res INT;
  SET res = add_func3(a, b, c) + d;
  if (c > 99) then
    return  3;
  else
    return res;
  end if;
END;
$$

DELIMITER ;

SELECT add_func4(1,2,3);
+------------------+
| add_func4(1,2,3) |
+------------------+
|                3 |
+------------------+

AGGREGATE

MariaDB starting with 10.3.3

From MariaDB 10.3.3, it is possible to create stored aggregate functions as well. See Stored Aggregate Functions for details.

RETURNS

The RETURNS clause specifies the return type of the function. NULL values are permitted with all return types.

What happens if the RETURN clause returns a value of a different type? It depends on the SQL_MODE in effect at the moment of the function creation.

If the SQL_MODE is strict (STRICT_ALL_TABLES or STRICT_TRANS_TABLES flags are specified), a 1366 error will be produced.

Otherwise, the value is coerced to the proper type. For example, if a function specifies an ENUM or SET value in the RETURNS clause, but the RETURN clause returns an integer, the value returned from the function is the string for the corresponding ENUM member of set of SET members.

MariaDB stores the SQL_MODE system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked.

LANGUAGE SQL

LANGUAGE SQL is a standard SQL clause, and it can be used in MariaDB for portability. However that clause has no meaning, because SQL is the only supported language for stored functions.

A function is deterministic if it can produce only one result for a given list of parameters. If the result may be affected by stored data, server variables, random numbers or any value that is not explicitly passed, then the function is not deterministic. Also, a function is non-deterministic if it uses non-deterministic functions like NOW() or CURRENT_TIMESTAMP(). The optimizer may choose a faster execution plan if it known that the function is deterministic. In such cases, you should declare the routine using the DETERMINISTIC keyword. If you want to explicitly state that the function is not deterministic (which is the default) you can use the NOT DETERMINISTIC keywords.

If you declare a non-deterministic function as DETERMINISTIC, you may get incorrect results. If you declare a deterministic function as NOT DETERMINISTIC, in some cases the queries will be slower.

OR REPLACE

MariaDB starting with 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION function_name ...;

with the exception that any existing privileges for the function are not dropped.

IF NOT EXISTS

MariaDB starting with 10.1.3

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the function already exists. Cannot be used together with OR REPLACE.

[NOT] DETERMINISTIC

The [NOT] DETERMINISTIC clause also affects binary logging, because the STATEMENT format can not be used to store or replicate non-deterministic statements.

CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default.

MODIFIES SQL DATA

MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL.

READS SQL DATA

READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed.

CONTAINS SQL

CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO.

NO SQL

NO SQL means nothing, because MariaDB does not currently support any language other than SQL.

Oracle Mode

MariaDB starting with 10.3

From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode.

Security

You must have the EXECUTE privilege on a function to call it. MariaDB automatically grants the EXECUTE and ALTER ROUTINE privileges to the account that called CREATE FUNCTION, even if the DEFINER clause was used.

Each function has an account associated as the definer. By default, the definer is the account that created the function. Use the DEFINER clause to specify a different account as the definer. You must have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, to use the DEFINER clause. See Account Names for details on specifying accounts.

The SQL SECURITY clause specifies what privileges are used when a function is called. If SQL SECURITY is INVOKER, the function body will be evaluated using the privileges of the user calling the function. If SQL SECURITY is DEFINER, the function body is always evaluated using the privileges of the definer account. DEFINER is the default.

This allows you to create functions that grant limited access to certain data. For example, say you have a table that stores some employee information, and that you've granted SELECT privileges only on certain columns to the user account roger.

CREATE TABLE employees (name TINYTEXT, dept TINYTEXT, salary INT);
GRANT SELECT (name, dept) ON employees TO roger;

To allow the user the get the maximum salary for a department, define a function and grant the EXECUTE privilege:

CREATE FUNCTION max_salary (dept TINYTEXT) RETURNS INT RETURN
  (SELECT MAX(salary) FROM employees WHERE employees.dept = dept);
GRANT EXECUTE ON FUNCTION max_salary TO roger;

Since SQL SECURITY defaults to DEFINER, whenever the user roger calls this function, the subselect will execute with your privileges. As long as you have privileges to select the salary of each employee, the caller of the function will be able to get the maximum salary for each department without being able to see individual salaries.

Character sets and collations

Function return types can be declared to use any valid character set and collation. If used, the COLLATE attribute needs to be preceded by a CHARACTER SET attribute.

If the character set and collation are not specifically set in the statement, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored function character set/collation will not be changed at the same time; the stored function needs to be dropped and recreated to ensure the same character set/collation as the database is used.

Examples

The following example function takes a parameter, performs an operation using an SQL function, and returns the result.

CREATE FUNCTION hello (s CHAR(20))
    RETURNS CHAR(50) DETERMINISTIC
    RETURN CONCAT('Hello, ',s,'!');

SELECT hello('world');
+----------------+
| hello('world') |
+----------------+
| Hello, world!  |
+----------------+

You can use a compound statement in a function to manipulate data with statements like INSERT and UPDATE. The following example creates a counter function that uses a temporary table to store the current value. Because the compound statement contains statements terminated with semicolons, you have to first change the statement delimiter with the DELIMITER statement to allow the semicolon to be used in the function body. See Delimiters in the mysql client for more.

CREATE TEMPORARY TABLE counter (c INT);
INSERT INTO counter VALUES (0);
DELIMITER //
CREATE FUNCTION counter () RETURNS INT
  BEGIN
    UPDATE counter SET c = c + 1;
    RETURN (SELECT c FROM counter LIMIT 1);
  END //
DELIMITER ;

Character set and collation:

CREATE FUNCTION hello2 (s CHAR(20))
  RETURNS CHAR(50) CHARACTER SET 'utf8' COLLATE 'utf8_bin' DETERMINISTIC
  RETURN CONCAT('Hello, ',s,'!');

See Also

CREATE PROCEDURE

Syntax

CREATE
    [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body

proc_parameter:
    [ IN | OUT | INOUT ] param_name type

type:
    Any valid MariaDB data type

characteristic:
    LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

routine_body:
    Valid SQL procedure statement

Description

Creates a stored procedure. By default, a routine is associated with the default database. To associate the routine explicitly with a given database, specify the name as db_name.sp_name when you create it.

When the routine is invoked, an implicit USE db_name is performed (and undone when the routine terminates). The causes the routine to have the given default database while it executes. USE statements within stored routines are disallowed.

When a stored procedure has been created, you invoke it by using the CALL statement (see CALL).

To execute the CREATE PROCEDURE statement, it is necessary to have the CREATE ROUTINE privilege. By default, MariaDB automatically grants the ALTER ROUTINE and EXECUTE privileges to the routine creator. See also Stored Routine Privileges.

The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at routine execution time, as described later. Requires the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege.

If the routine name is the same as the name of a built-in SQL function, you must use a space between the name and the following parenthesis when defining the routine, or a syntax error occurs. This is also true when you invoke the routine later. For this reason, we suggest that it is better to avoid re-using the names of existing SQL functions for your own stored routines.

The IGNORE_SPACE SQL mode applies to built-in functions, not to stored routines. It is always allowable to have spaces after a routine name, regardless of whether IGNORE_SPACE is enabled.

The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive.

Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used.

For valid identifiers to use as procedure names, see Identifier Names.

IN/OUT/INOUT

Each parameter is an IN parameter by default. To specify otherwise for a parameter, use the keyword OUT or INOUT before the parameter name.

An IN parameter passes a value into a procedure. The procedure might modify the value, but the modification is not visible to the caller when the procedure returns. An OUT parameter passes a value from the procedure back to the caller. Its initial value is NULL within the procedure, and its value is visible to the caller when the procedure returns. An INOUT parameter is initialized by the caller, can be modified by the procedure, and any change made by the procedure is visible to the caller when the procedure returns.

For each OUT or INOUT parameter, pass a user-defined variable in the CALL statement that invokes the procedure so that you can obtain its value when the procedure returns. If you are calling the procedure from within another stored procedure or function, you can also pass a routine parameter or local routine variable as an IN or INOUT parameter.

DETERMINISTIC/NOT DETERMINISTIC

DETERMINISTIC and NOT DETERMINISTIC apply only to functions. Specifying DETERMINISTC or NON-DETERMINISTIC in procedures has no effect. The default value is NOT DETERMINISTIC. Functions are DETERMINISTIC when they always return the same value for the same input. For example, a truncate or substring function. Any function involving data, therefore, is always NOT DETERMINISTIC.

CONTAINS SQL/NO SQL/READS SQL DATA/MODIFIES SQL DATA

CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default.

MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL.

READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed.

CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO.

NO SQL means nothing, because MariaDB does not currently support any language other than SQL.

The routine_body consists of a valid SQL procedure statement. This can be a simple statement such as SELECT or INSERT, or it can be a compound statement written using BEGIN and END. Compound statements can contain declarations, loops, and other control structure statements. See Programmatic and Compound Statements for syntax details.

MariaDB allows routines to contain DDL statements, such as CREATE and DROP. MariaDB also allows stored procedures (but not stored functions) to contain SQL transaction statements such as COMMIT.

For additional information about statements that are not allowed in stored routines, see Stored Routine Limitations.

Invoking stored procedure from within programs

For information about invoking stored procedures from within programs written in a language that has a MariaDB/MySQL interface, see CALL.

OR REPLACE

MariaDB starting with 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP PROCEDURE IF EXISTS name;
CREATE PROCEDURE name ...;

with the exception that any existing privileges for the procedure are not dropped.

sql_mode

MariaDB stores the sql_mode system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked.

Character Sets and Collations

Procedure parameters can be declared with any character set/collation. If the character set and collation are not specifically set, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored procedure character set/collation will not be changed at the same time; the stored procedure needs to be dropped and recreated to ensure the same character set/collation as the database is used.

Oracle Mode

MariaDB starting with 10.3

From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode.

Examples

The following example shows a simple stored procedure that uses an OUT parameter. It uses the DELIMITER command to set a new delimiter for the duration of the process see Delimiters in the mysql client.

DELIMITER //

CREATE PROCEDURE simpleproc (OUT param1 INT)
 BEGIN
  SELECT COUNT(*) INTO param1 FROM t;
 END;
//

DELIMITER ;

CALL simpleproc(@a);

SELECT @a;
+------+
| @a   |
+------+
|    1 |
+------+

Character set and collation:

DELIMITER //

CREATE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//

DELIMITER ;

CREATE OR REPLACE:

DELIMITER //

CREATE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists

DELIMITER ;

DELIMITER //

CREATE OR REPLACE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists

DELIMITER ;
Query OK, 0 rows affected (0.03 sec)

See Also

ST_UNION

Syntax

ST_UNION(g1,g2)

Description

Returns a geometry that is the union of the geometry g1 and geometry g2.

Examples

SET @g1 = GEOMFROMTEXT('POINT (0 2)');

SET @g2 = GEOMFROMTEXT('POINT (2 0)');

SELECT ASTEXT(ST_UNION(@g1,@g2));
+---------------------------+
| ASTEXT(ST_UNION(@g1,@g2)) |
+---------------------------+
| MULTIPOINT(2 0,0 2)       |
+---------------------------+
SET @g1 = GEOMFROMTEXT('POLYGON((0 0,0 3,3 3,3 0,0 0))');

SET @g2 = GEOMFROMTEXT('POLYGON((2 2,4 2,4 4,2 4,2 2))');

SELECT ASTEXT(ST_UNION(@g1,@g2));
+------------------------------------------------+
| ASTEXT(ST_UNION(@g1,@g2))                      |
+------------------------------------------------+
| POLYGON((0 0,0 3,2 3,2 4,4 4,4 2,3 2,3 0,0 0)) |
+------------------------------------------------+

CACHE INDEX

Syntax

CACHE INDEX                      
  tbl_index_list [, tbl_index_list] ...
  IN key_cache_name                    

tbl_index_list:
  tbl_name [[INDEX|KEY] (index_name[, index_name] ...)]

Description

The CACHE INDEX statement assigns table indexes to a specific key cache. It is used only for MyISAM tables.

A default key cache exists and cannot be destroyed. To create more key caches, the key_buffer_size server system variable.

The associations between tables indexes and key caches are lost on server restart. To recreate them automatically, it is necessary to configure caches in a configuration file and include some CACHE INDEX (and optionally LOAD INDEX) statements in the init file.

Examples

The following statement assigns indexes from the tables t1, t2, and t3 to the key cache named hot_cache:

CACHE INDEX t1, t2, t3 IN hot_cache;
+---------+--------------------+----------+----------+
| Table   | Op                 | Msg_type | Msg_text |
+---------+--------------------+----------+----------+
| test.t1 | assign_to_keycache | status   | OK       |
| test.t2 | assign_to_keycache | status   | OK       |
| test.t3 | assign_to_keycache | status   | OK       |
+---------+--------------------+----------+----------+

Implementation (for MyISAM)

Normally CACHE INDEX should not take a long time to execute. Internally it's implemented the following way:

  • Find the right key cache (under LOCK_global_system_variables)
  • Open the table with a TL_READ_NO_INSERT lock.
  • Flush the original key cache for the given file (under key cache lock)
  • Flush the new key cache for the given file (safety)
  • Move the file to the new key cache (under file share lock)

The only possible long operations are getting the locks for the table and flushing the original key cache, if there were many key blocks for the file in it.

We plan to also add CACHE INDEX for Aria tables if there is a need for this.

HELP Command

Syntax

HELP search_string

Description

The HELP command can be used in any MariaDB client, such as the mysql command-line client, to get basic syntax help and a short description for most commands and functions.

If you provide an argument to the HELP command, the mysql client uses it as a search string to access server-side help. The proper operation of this command requires that the help tables in the mysql database be initialized with help topic information.

If there is no match for the search string, the search fails. Use HELP contents to see a list of the help categories:

HELP contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Compound Statements
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Functions and Modifiers for Use with GROUP BY
   Geographic Features
   Help Metadata
   Language Structure
   Plugins
   Procedures
   Sequences
   Table Maintenance
   Transactions
   User-Defined Functions
   Utility

If a search string matches multiple items, MariaDB shows a list of matching topics:

HELP drop
Many help items for your request exist.
To make a more specific request, please type 'help <item>',
where <item> is one of the following
topics:
   ALTER TABLE
   DROP DATABASE
   DROP EVENT
   DROP FUNCTION
   DROP FUNCTION UDF
   DROP INDEX
   DROP PACKAGE
   DROP PACKAGE BODY
   DROP PROCEDURE
   DROP ROLE
   DROP SEQUENCE
   DROP SERVER
   DROP TABLE
   DROP TRIGGER
   DROP USER
   DROP VIEW

Then you can enter a topic as the search string to see the help entry for that topic.

The help is provided with the MariaDB server and makes use of four help tables found in the mysql database: help_relation, help_topic, help_category and help_keyword. These tables are populated by the mysql_install_db or fill_help_table.sql scripts which, until MariaDB 10.4.7, contain data generated from an old version of MySQL.

CREATE TABLESPACE

The CREATE TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

KILL [CONNECTION | QUERY]

Syntax

KILL [HARD | SOFT] [CONNECTION | QUERY [ID] ] [thread_id | USER user_name | query_id]

Description

Each connection to mysqld runs in a separate thread. You can see which threads are running with the SHOW PROCESSLIST statement and kill a thread with the KILL thread_id statement. KILL allows the optional CONNECTION or QUERY modifier:

  • KILL CONNECTION is the same as KILL with no modifier: It terminates the connection associated with the given thread or query id.
  • KILL QUERY terminates the statement that the connection thread_id is currently executing, but leaves the connection itself intact.
  • KILL QUERY ID (introduced in MariaDB 10.0.5) terminates the query by query_id, leaving the connection intact.

If a connection is terminated that has an active transaction, the transaction will be rolled back. If only a query is killed, the current transaction will stay active. See also idle_transaction_timeout.

If you have the PROCESS privilege, you can see all threads. If you have the SUPER privilege, or, from MariaDB 10.5.2, the CONNECTION ADMIN privilege, you can kill all threads and statements. Otherwise, you can see and kill only your own threads and statements.

Killing queries that repair or create indexes on MyISAM and Aria tables may result in corrupted tables. Use the SOFT option to avoid this!

The HARD option (default) kills a command as soon as possible. If you use SOFT, then critical operations that may leave a table in an inconsistent state will not be interrupted. Such operations include REPAIR and INDEX creation for MyISAM and Aria tables (REPAIR TABLE, OPTIMIZE TABLE).

KILL ... USER username will kill all connections/queries for a given user. USER can be specified one of the following ways:

If you specify a thread id and that thread does not exist, you get the following error:

ERROR 1094 (HY000): Unknown thread id: <thread_id>

If you specify a query id that doesn't exist, you get the following error:

ERROR 1957 (HY000): Unknown query id: <query_id>

However, if you specify a user name, no error is issued for non-connected (or even non-existing) users. To check if the connection/query has been killed, you can use the ROW_COUNT() function.

A client whose connection is killed receives the following error:

ERROR 1317 (70100): Query execution was interrupted

To obtain a list of existing sessions, use the SHOW PROCESSLIST statement or query the Information Schema PROCESSLIST table.

Note: You cannot use KILL with the Embedded MySQL Server library because the embedded server merely runs inside the threads of the host application. It does not create any connection threads of its own.

Note: You can also use mysqladmin kill thread_id [,thread_id...] to kill connections. To get a list of running queries, use mysqladmin processlist. See mysqladmin.

Percona Toolkit contains a program, pt-kill that can be used to automatically kill connections that match certain criteria. For example, it can be used to terminate idle connections, or connections that have been busy for more than 60 seconds.

See Also

RESET

Syntax

RESET reset_option [, reset_option] ...

Description

The RESET statement is used to clear the state of various server operations. You must have the RELOAD privilege to execute RESET.

RESET acts as a stronger version of the FLUSH statement.

The different RESET options are:

OptionDescription
SLAVE ["connection_name"] [ALL]Deletes all relay logs from the slave and reset the replication position in the master binary log.
MASTERDeletes all old binary logs, makes the binary index file (--log-bin-index) empty and creates a new binary log file. This is useful when you want to reset the master to an initial state. If you want to just delete old, not used binary logs, you should use the PURGE BINARY LOGS command.
QUERY CACHERemoves all queries from the query cache. See also FLUSH QUERY CACHE.

CREATE VIEW

Syntax

CREATE
    [OR REPLACE]
    [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    [SQL SECURITY { DEFINER | INVOKER }]
    VIEW [IF NOT EXISTS] view_name [(column_list)]
    AS select_statement
    [WITH [CASCADED | LOCAL] CHECK OPTION]

Description

The CREATE VIEW statement creates a new view, or replaces an existing one if the OR REPLACE clause is given. If the view does not exist, CREATE OR REPLACE VIEW is the same as CREATE VIEW. If the view does exist, CREATE OR REPLACE VIEW is the same as ALTER VIEW.

The select_statement is a SELECT statement that provides the definition of the view. (When you select from the view, you select in effect using the SELECT statement.) select_statement can select from base tables or other views.

The view definition is "frozen" at creation time, so changes to the underlying tables afterwards do not affect the view definition. For example, if a view is defined as SELECT * on a table, new columns added to the table later do not become part of the view. A SHOW CREATE VIEW shows that such queries are rewritten and column names are included in the view definition.

The view definition must be a query that does not return errors at view creation times. However, the base tables used by the views might be altered later and the query may not be valid anymore. In this case, querying the view will result in an error. CHECK TABLE helps in finding this kind of problems.

The ALGORITHM clause affects how MariaDB processes the view. The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at view invocation time. The WITH CHECK OPTION clause can be given to constrain inserts or updates to rows in tables referenced by the view. These clauses are described later in this section.

The CREATE VIEW statement requires the CREATE VIEW privilege for the view, and some privilege for each column selected by the SELECT statement. For columns used elsewhere in the SELECT statement you must have the SELECT privilege. If the OR REPLACE clause is present, you must also have the DROP privilege for the view.

A view belongs to a database. By default, a new view is created in the default database. To create the view explicitly in a given database, specify the name as db_name.view_name when you create it.

CREATE VIEW test.v AS SELECT * FROM t;

Base tables and views share the same namespace within a database, so a database cannot contain a base table and a view that have the same name.

Views must have unique column names with no duplicates, just like base tables. By default, the names of the columns retrieved by the SELECT statement are used for the view column names. To define explicit names for the view columns, the optional column_list clause can be given as a list of comma-separated identifiers. The number of names in column_list must be the same as the number of columns retrieved by the SELECT statement.

MySQL until 5.1.28

Prior to MySQL 5.1.29, When you modify an existing view, the current view definition is backed up and saved. It is stored in that table's database directory, in a subdirectory named arc. The backup file for a view v is named v.frm-00001. If you alter the view again, the next backup is named v.frm-00002. The three latest view backup definitions are stored. Backed up view definitions are not preserved by mysqldump, or any other such programs, but you can retain them using a file copy operation. However, they are not needed for anything but to provide you with a backup of your previous view definition. It is safe to remove these backup definitions, but only while mysqld is not running. If you delete the arc subdirectory or its files while mysqld is running, you will receive an error the next time you try to alter the view:

MariaDB [test]> ALTER VIEW v AS SELECT * FROM t; 
ERROR 6 (HY000): Error on delete of '.\test\arc/v.frm-0004' (Errcode: 2)

Columns retrieved by the SELECT statement can be simple references to table columns. They can also be expressions that use functions, constant values, operators, and so forth.

Unqualified table or view names in the SELECT statement are interpreted with respect to the default database. A view can refer to tables or views in other databases by qualifying the table or view name with the proper database name.

A view can be created from many kinds of SELECT statements. It can refer to base tables or other views. It can use joins, UNION, and subqueries. The SELECT need not even refer to any tables. The following example defines a view that selects two columns from another table, as well as an expression calculated from those columns:

CREATE TABLE t (qty INT, price INT);

INSERT INTO t VALUES(3, 50);

CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;

SELECT * FROM v;
+------+-------+-------+
| qty  | price | value |
+------+-------+-------+
|    3 |    50 |   150 |
+------+-------+-------+

A view definition is subject to the following restrictions:

  • The SELECT statement cannot contain a subquery in the FROM clause.
  • The SELECT statement cannot refer to system or user variables.
  • Within a stored program, the definition cannot refer to program parameters or local variables.
  • The SELECT statement cannot refer to prepared statement parameters.
  • Any table or view referred to in the definition must exist. However, after a view has been created, it is possible to drop a table or view that the definition refers to. In this case, use of the view results in an error. To check a view definition for problems of this kind, use the CHECK TABLE statement.
  • The definition cannot refer to a TEMPORARY table, and you cannot create a TEMPORARY view.
  • Any tables named in the view definition must exist at definition time.
  • You cannot associate a trigger with a view.
  • For valid identifiers to use as view names, see Identifier Names.

ORDER BY is allowed in a view definition, but it is ignored if you select from a view using a statement that has its own ORDER BY.

For other options or clauses in the definition, they are added to the options or clauses of the statement that references the view, but the effect is undefined. For example, if a view definition includes a LIMIT clause, and you select from the view using a statement that has its own LIMIT clause, it is undefined which limit applies. This same principle applies to options such as ALL, DISTINCT, or SQL_SMALL_RESULT that follow the SELECT keyword, and to clauses such as INTO, FOR UPDATE, and LOCK IN SHARE MODE.

The PROCEDURE clause cannot be used in a view definition, and it cannot be used if a view is referenced in the FROM clause.

If you create a view and then change the query processing environment by changing system variables, that may affect the results that you get from the view:

CREATE VIEW v (mycol) AS SELECT 'abc';

SET sql_mode = '';

SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| mycol | 
+-------+

SET sql_mode = 'ANSI_QUOTES';

SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| abc   | 
+-------+

The DEFINER and SQL SECURITY clauses determine which MariaDB account to use when checking access privileges for the view when a statement is executed that references the view. They were added in MySQL 5.1.2. The legal SQL SECURITY characteristic values are DEFINER and INVOKER. These indicate that the required privileges must be held by the user who defined or invoked the view, respectively. The default SQL SECURITY value is DEFINER.

If a user value is given for the DEFINER clause, it should be a MariaDB account in 'user_name'@'host_name' format (the same format used in the GRANT statement). The user_name and host_name values both are required. The definer can also be given as CURRENT_USER or CURRENT_USER(). The default DEFINER value is the user who executes the CREATE VIEW statement. This is the same as specifying DEFINER = CURRENT_USER explicitly.

If you specify the DEFINER clause, these rules determine the legal DEFINER user values:

  • If you do not have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, the only legal user value is your own account, either specified literally or by using CURRENT_USER. You cannot set the definer to some other account.
  • If you have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, you can specify any syntactically legal account name. If the account does not actually exist, a warning is generated.
  • If the SQL SECURITY value is DEFINER but the definer account does not exist when the view is referenced, an error occurs.

Within a view definition, CURRENT_USER returns the view's DEFINER value by default. For views defined with the SQL SECURITY INVOKER characteristic, CURRENT_USER returns the account for the view's invoker. For information about user auditing within views, see http://dev.mysql.com/doc/refman/5.1/en/account-activity-auditing.html.

Within a stored routine that is defined with the SQL SECURITY DEFINER characteristic, CURRENT_USER returns the routine's DEFINER value. This also affects a view defined within such a program, if the view definition contains a DEFINER value of CURRENT_USER.

View privileges are checked like this:

  • At view definition time, the view creator must have the privileges needed to use the top-level objects accessed by the view. For example, if the view definition refers to table columns, the creator must have privileges for the columns, as described previously. If the definition refers to a stored function, only the privileges needed to invoke the function can be checked. The privileges required when the function runs can be checked only as it executes: For different invocations of the function, different execution paths within the function might be taken.
  • When a view is referenced, privileges for objects accessed by the view are checked against the privileges held by the view creator or invoker, depending on whether the SQL SECURITY characteristic is DEFINER or INVOKER, respectively.
  • If reference to a view causes execution of a stored function, privilege checking for statements executed within the function depend on whether the function is defined with a SQL SECURITY characteristic of DEFINER or INVOKER. If the security characteristic is DEFINER, the function runs with the privileges of its creator. If the characteristic is INVOKER, the function runs with the privileges determined by the view's SQL SECURITY characteristic.

Example: A view might depend on a stored function, and that function might invoke other stored routines. For example, the following view invokes a stored function f():

CREATE VIEW v AS SELECT * FROM t WHERE t.id = f(t.name);

Suppose that f() contains a statement such as this:

IF name IS NULL then
  CALL p1();
ELSE
  CALL p2();
END IF;

The privileges required for executing statements within f() need to be checked when f() executes. This might mean that privileges are needed for p1() or p2(), depending on the execution path within f(). Those privileges must be checked at runtime, and the user who must possess the privileges is determined by the SQL SECURITY values of the view v and the function f().

The DEFINER and SQL SECURITY clauses for views are extensions to standard SQL. In standard SQL, views are handled using the rules for SQL SECURITY INVOKER.

If you invoke a view that was created before MySQL 5.1.2, it is treated as though it was created with a SQL SECURITY DEFINER clause and with a DEFINER value that is the same as your account. However, because the actual definer is unknown, MySQL issues a warning. To make the warning go away, it is sufficient to re-create the view so that the view definition includes a DEFINER clause.

The optional ALGORITHM clause is an extension to standard SQL. It affects how MariaDB processes the view. ALGORITHM takes three values: MERGE, TEMPTABLE, or UNDEFINED. The default algorithm is UNDEFINED if no ALGORITHM clause is present. See View Algorithms for more information.

Some views are updatable. That is, you can use them in statements such as UPDATE, DELETE, or INSERT to update the contents of the underlying table. For a view to be updatable, there must be a one-to-one relationship between the rows in the view and the rows in the underlying table. There are also certain other constructs that make a view non-updatable. See Inserting and Updating with Views.

WITH CHECK OPTION

The WITH CHECK OPTION clause can be given for an updatable view to prevent inserts or updates to rows except those for which the WHERE clause in the select_statement is true.

In a WITH CHECK OPTION clause for an updatable view, the LOCAL and CASCADED keywords determine the scope of check testing when the view is defined in terms of another view. The LOCAL keyword restricts the CHECK OPTION only to the view being defined. CASCADED causes the checks for underlying views to be evaluated as well. When neither keyword is given, the default is CASCADED.

For more information about updatable views and the WITH CHECK OPTION clause, see Inserting and Updating with Views.

IF NOT EXISTS

MariaDB starting with 10.1.3

The IF NOT EXISTS clause was added in MariaDB 10.1.3

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified view already exists. Cannot be used together with the OR REPLACE clause.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE VIEW is atomic.

Examples

CREATE TABLE t (a INT, b INT) ENGINE = InnoDB;

INSERT INTO t VALUES (1,1), (2,2), (3,3);

CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;

SELECT * FROM v;
+------+------+
| a    | a2   |
+------+------+
|    1 |    2 |
|    2 |    4 |
|    3 |    6 |
+------+------+

OR REPLACE and IF NOT EXISTS:

CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;
ERROR 1050 (42S01): Table 'v' already exists

CREATE OR REPLACE VIEW v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected (0.04 sec)

CREATE VIEW IF NOT EXISTS v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+--------------------------+
| Level | Code | Message                  |
+-------+------+--------------------------+
| Note  | 1050 | Table 'v' already exists |
+-------+------+--------------------------+

See Also

DROP PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

DROP PACKAGE [IF EXISTS]  [ db_name . ] package_name

Description

The DROP PACKAGE statement can be used when Oracle SQL_MODE is set.

The DROP PACKAGE statement drops a stored package entirely:

  • Drops the package specification (earlier created using the CREATE PACKAGE statement).
  • Drops the package implementation, if the implementation was already created using the CREATE PACKAGE BODY statement.

See Also

DROP PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

DROP PACKAGE BODY [IF EXISTS]  [ db_name . ] package_name

Description

The DROP PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

The DROP PACKAGE BODY statement drops the package body (i.e the implementation), previously created using the CREATE PACKAGE BODY statement.

Note, DROP PACKAGE BODY drops only the package implementation, but does not drop the package specification. Use DROP PACKAGE to drop the package entirely (i.e. both implementation and specification).

See also

DROP TABLESPACE

The DROP TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

LASTVAL

LASTVAL is a synonym for PREVIOUS VALUE for sequence_name.

NEXTVAL

NEXTVAL is a synonym for NEXT VALUE for sequence_name.

JSON_ARRAY

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_ARRAY([value[, value2] ...])

Description

Returns a JSON array containing the listed values. The list can be empty.

Example

SELECT Json_Array(56, 3.1416, 'My name is "Foo"', NULL);
+--------------------------------------------------+
| Json_Array(56, 3.1416, 'My name is "Foo"', NULL) |
+--------------------------------------------------+
| [56, 3.1416, "My name is \"Foo\"", null]         |
+--------------------------------------------------+

See also

JSON_COMPACT

MariaDB starting with 10.2.4

This function was added in MariaDB 10.2.4.

Syntax

JSON_COMPACT(json_doc)

Description

Removes all unnecessary spaces so the json document is as short as possible.

Example

SET @j = '{ "A": 1, "B": [2, 3]}';

SELECT JSON_COMPACT(@j), @j;
+-------------------+------------------------+
| JSON_COMPACT(@j)  | @j                     |
+-------------------+------------------------+
| {"A":1,"B":[2,3]} | { "A": 1, "B": [2, 3]} |
+-------------------+------------------------+

See Also

JSON_DETAILED

MariaDB starting with 10.2.4

This function was added in MariaDB 10.2.4.

Syntax

JSON_DETAILED(json_doc[, tab_size])

Description

Represents JSON in the most understandable way emphasizing nested structures.

Example

SET @j = '{ "A":1,"B":[2,3]}';

SELECT @j;
+--------------------+
| @j                 |
+--------------------+
| { "A":1,"B":[2,3]} |
+--------------------+

SELECT JSON_DETAILED(@j);
+------------------------------------------------------------+
| JSON_DETAILED(@j)                                          |
+------------------------------------------------------------+
| {
    "A": 1,
    "B": 
    [
        2,
        3
    ]
} |
+------------------------------------------------------------+

See Also

JSON_LOOSE

MariaDB starting with 10.2.4

This function was added in MariaDB 10.2.4.

Syntax

JSON_LOOSE(json_doc)

Description

Adds spaces to a JSON document to make it look more readable.

Example

SET @j = '{ "A":1,"B":[2,3]}';

SELECT JSON_LOOSE(@j), @j;
+-----------------------+--------------------+
| JSON_LOOSE(@j)        | @j                 |
+-----------------------+--------------------+
| {"A": 1, "B": [2, 3]} | { "A":1,"B":[2,3]} |
+-----------------------+--------------------+

JSON_MERGE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_MERGE(json_doc, json_doc[, json_doc] ...)

Description

Merges the given JSON documents.

Returns the merged result,or NULL if any argument is NULL.

An error occurs if any of the arguments are not valid JSON documents.

JSON_MERGE has been deprecated since MariaDB 10.2.25, MariaDB 10.3.16 and MariaDB 10.4.5. JSON_MERGE_PATCH is an RFC 7396-compliant replacement, and JSON_MERGE_PRESERVE is a synonym.

Example

SET @json1 = '[1, 2]';
SET @json2 = '[3, 4]';

SELECT JSON_MERGE(@json1,@json2);
+---------------------------+
| JSON_MERGE(@json1,@json2) |
+---------------------------+
| [1, 2, 3, 4]              |
+---------------------------+

See Also

JSON_OBJECT

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_OBJECT([key, value[, key, value] ...])

Description

Returns a JSON object containing the given key/value pairs. The key/value list can be empty.

An error will occur if there are an odd number of arguments, or any key name is NULL.

Example

SELECT JSON_OBJECT("id", 1, "name", "Monty");
+---------------------------------------+
| JSON_OBJECT("id", 1, "name", "Monty") |
+---------------------------------------+
| {"id": 1, "name": "Monty"}            |
+---------------------------------------+

See also

JSON_SET

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_SET(json_doc, path, val[, path, val] ...)

Description

Updates or inserts data into a JSON document, returning the result, or NULL if any of the arguments are NULL or the optional path fails to find an object.

An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or wildcard.

JSON_SET can update or insert data, while JSON_REPLACE can only update, and JSON_INSERT only insert.

Examples

SELECT JSON_SET(Priv, '$.locked', 'true') FROM mysql.global_priv

CUME_DIST

MariaDB starting with 10.2

The CUME_DIST() function was first introduced with window functions in MariaDB 10.2.0.

Syntax

CUME_DIST() OVER ( 
  [ PARTITION BY partition_expression ] 
  [ ORDER BY order_list ]
)

Description

CUME_DIST() is a window function that returns the cumulative distribution of a given row. The following formula is used to calculate the value:

(number of rows <= current row) / (total rows)

Examples

create table t1 (
  pk int primary key,
  a int,
  b int
);


insert into t1 values
( 1 , 0, 10),
( 2 , 0, 10),
( 3 , 1, 10),
( 4 , 1, 10),
( 8 , 2, 10),
( 5 , 2, 20),
( 6 , 2, 20),
( 7 , 2, 20),
( 9 , 4, 20),
(10 , 4, 20);

select pk, a, b,
    rank() over (order by a) as rank,
    percent_rank() over (order by a) as pct_rank,
    cume_dist() over (order by a) as cume_dist
from t1;
+----+------+------+------+--------------+--------------+
| pk | a    | b    | rank | pct_rank     | cume_dist    |
+----+------+------+------+--------------+--------------+
|  1 |    0 |   10 |    1 | 0.0000000000 | 0.2000000000 |
|  2 |    0 |   10 |    1 | 0.0000000000 | 0.2000000000 |
|  3 |    1 |   10 |    3 | 0.2222222222 | 0.4000000000 |
|  4 |    1 |   10 |    3 | 0.2222222222 | 0.4000000000 |
|  5 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  6 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  7 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  8 |    2 |   10 |    5 | 0.4444444444 | 0.8000000000 |
|  9 |    4 |   20 |    9 | 0.8888888889 | 1.0000000000 |
| 10 |    4 |   20 |    9 | 0.8888888889 | 1.0000000000 |
+----+------+------+------+--------------+--------------+

select pk, a, b,
       percent_rank() over (order by pk) as pct_rank,
       cume_dist() over (order by pk) as cume_dist
from t1 order by pk;
+----+------+------+--------------+--------------+
| pk | a    | b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 0.1000000000 |
|  2 |    0 |   10 | 0.1111111111 | 0.2000000000 |
|  3 |    1 |   10 | 0.2222222222 | 0.3000000000 |
|  4 |    1 |   10 | 0.3333333333 | 0.4000000000 |
|  5 |    2 |   20 | 0.4444444444 | 0.5000000000 |
|  6 |    2 |   20 | 0.5555555556 | 0.6000000000 |
|  7 |    2 |   20 | 0.6666666667 | 0.7000000000 |
|  8 |    2 |   10 | 0.7777777778 | 0.8000000000 |
|  9 |    4 |   20 | 0.8888888889 | 0.9000000000 |
| 10 |    4 |   20 | 1.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

select pk, a, b,
        percent_rank() over (partition by a order by a) as pct_rank,
        cume_dist() over (partition by a order by a) as cume_dist
from t1;
+----+------+------+--------------+--------------+
| pk | a    | b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  2 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  3 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  4 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  5 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  6 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  7 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  8 |    2 |   10 | 0.0000000000 | 1.0000000000 |
|  9 |    4 |   20 | 0.0000000000 | 1.0000000000 |
| 10 |    4 |   20 | 0.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

See Also

NTH_VALUE

MariaDB starting with 10.2.2

The NTH_VALUE() function was first introduced with other window functions in MariaDB 10.2.

Syntax

NTH_VALUE (expr[, num_row]) OVER ( 
  [ PARTITION BY partition_expression ] 
  [ ORDER BY order_list ]
)

Contents

  1. Syntax
  2. Description

Description

The NTH_VALUE function returns the value evaluated at row number num_row of the window frame, starting from 1, or NULL if the row does not exist.

SPIDER_FLUSH_TABLE_MON_CACHE

Syntax

SPIDER_FLUSH_TABLE_MON_CACHE()

Description

A UDF installed with the Spider Storage Engine, this function is used for refreshing monitoring server information. It returns a value of 1.

Examples

SELECT SPIDER_FLUSH_TABLE_MON_CACHE();
+--------------------------------+
| SPIDER_FLUSH_TABLE_MON_CACHE() |
+--------------------------------+
|                              1 |
+--------------------------------+

COLUMN_CHECK

Syntax

COLUMN_CHECK(dyncol_blob);

Description

Check if dyncol_blob is a valid packed dynamic columns blob. Return value of 1 means the blob is valid, return value of 0 means it is not.

Rationale: Normally, one works with valid dynamic column blobs. Functions like COLUMN_CREATE, COLUMN_ADD, COLUMN_DELETE always return valid dynamic column blobs. However, if a dynamic column blob is accidentally truncated, or transcoded from one character set to another, it will be corrupted. This function can be used to check if a value in a blob field is a valid dynamic column blob.

COLUMN_DELETE

Syntax

COLUMN_DELETE(dyncol_blob, column_nr, column_nr...);
COLUMN_DELETE(dyncol_blob, column_name, column_name...);

Description

Deletes a dynamic column with the specified name. Multiple names can be given. The return value is a dynamic column blob after the modification.

COLUMN_EXISTS

Syntax

COLUMN_EXISTS(dyncol_blob, column_nr);
COLUMN_EXISTS(dyncol_blob, column_name);

Description

Checks if a column with name column_name exists in dyncol_blob. If yes, return 1, otherwise return 0. See dynamic columns for more information.

COLUMN_LIST

Syntax

COLUMN_LIST(dyncol_blob);

Description

Returns a comma-separated list of column names. The names are quoted with backticks.

See dynamic columns for more information.

CALL

Syntax

CALL sp_name([parameter[,...]])
CALL sp_name[()]

Description

The CALL statement invokes a stored procedure that was defined previously with CREATE PROCEDURE.

Stored procedure names can be specified as database_name.procedure_name. Procedure names and database names can be quoted with backticks (). This is necessary if they are reserved words, or contain special characters. See identifier qualifiers for details.

CALL p() and CALL p are equivalent.

If parentheses are used, any number of spaces, tab characters and newline characters are allowed between the procedure's name and the open parenthesis.

CALL can pass back values to its caller using parameters that are declared as OUT or INOUT parameters. If no value is assigned to an OUT parameter, NULL is assigned (and its former value is lost). To pass such values from another stored program you can use user-defined variables, local variables or routine's parameters; in other contexts, you can only use user-defined variables.

CALL can also be executed as a prepared statement. Placeholders can be used for IN parameters in all versions of MariaDB; for OUT and INOUT parameters, placeholders can be used since MariaDB 5.5.

When the procedure returns, a client program can also obtain the number of rows affected for the final statement executed within the routine: At the SQL level, call the ROW_COUNT() function; from the C API, call the mysql_affected_rows() function.

If the CLIENT_MULTI_RESULTS API flag is set, CALL can return any number of resultsets and the called stored procedure can execute prepared statements. If it is not set, at most one resultset can be returned and prepared statements cannot be used within procedures.

Concurrent Inserts

Contents

  1. Notes
  2. See Also

The MyISAM storage engine supports concurrent inserts. This feature allows SELECT statements to be executed during INSERT operations, reducing contention.

Whether concurrent inserts can be used or not depends on the value of the concurrent_insert server system variable:

  • NEVER (0) disables concurrent inserts.
  • AUTO (1) allows concurrent inserts only when the target table has no free blocks (no data in the middle of the table has been deleted after the last OPTIMIZE TABLE). This is the default.
  • ALWAYS (2) always enables concurrent inserts, in which case new rows are added at the end of a table if the table is being used by another thread.

If the binary log is used, CREATE TABLE ... SELECT and INSERT ... SELECT statements cannot use concurrent inserts. These statements acquire a read lock on the table, so concurrent inserts will need to wait. This way the log can be safely used to restore data.

Concurrent inserts are not used by replicas with the row based replication (see binary log formats).

If an INSERT statement contain the HIGH_PRIORITY clause, concurrent inserts cannot be used. INSERT ... DELAYED is usually unneeded if concurrent inserts are enabled.

LOAD DATA INFILE uses concurrent inserts if the CONCURRENT keyword is specified and concurrent_insert is not NEVER. This makes the statement slower (even if no other sessions access the table) but reduces contention.

LOCK TABLES allows non-conflicting concurrent inserts if a READ LOCAL lock is used. Concurrent inserts are not allowed if the LOCAL keyword is omitted.

Notes

The decision to enable concurrent insert for a table is done when the table is opened. If you change the value of concurrent_insert it will only affect new opened tables. If you want it to work for also for tables in use or cached, you should do FLUSH TABLES after setting the variable.

See Also

EXCEPT

MariaDB starting with 10.3.0

EXCEPT was introduced in MariaDB 10.3.0.

The result of EXCEPT is all records of the left SELECT result set except records which are in right SELECT result set, i.e. it is subtraction of two result sets. From MariaDB 10.6.1, MINUS is a synonym.

Syntax

SELECT ...
(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Please note:

  • Brackets for explicit operation precedence are not supported; use a subquery in the FROM clause as a workaround).

Description

MariaDB has supported EXCEPT and INTERSECT in addition to UNION since MariaDB 10.3.

All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION.

EXCEPT implicitly supposes a DISTINCT operation.

The result of EXCEPT is all records of the left SELECT result except records which are in right SELECT result set, i.e. it is subtraction of two result sets.

EXCEPT and UNION have the same operation precedence and INTERSECT has a higher precedence, unless running in Oracle mode, in which case all three have the same precedence.

MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

MariaDB starting with 10.5.0

ALL/DISTINCT

EXCEPT ALL and EXCEPT DISTINCT were introduced in MariaDB 10.5.0. The ALL operator leaves duplicates intact, while the DISTINCT operator removes duplicates. DISTINCT is the default behavior if neither operator is supplied, and the only behavior prior to MariaDB 10.5.

Examples

Show customers which are not employees:

(SELECT e_name AS name, email FROM customers)
EXCEPT
(SELECT c_name AS name, email FROM employees);

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) EXCEPT (SELECT c FROM t3);
+------+
| a    |
+------+
|    2 |
|    3 |
|    4 |
|    5 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) EXCEPT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
+------+

See Also

HIGH_PRIORITY and LOW_PRIORITY

Contents

  1. See Also

The InnoDB storage engine uses row-level locking to ensure data integrity. However some storage engines (such as MEMORY, MyISAM, Aria and MERGE) lock the whole table to prevent conflicts. These storage engines use two separate queues to remember pending statements; one is for SELECTs and the other one is for write statements (INSERT, DELETE, UPDATE). By default, the latter has a higher priority.

To give write operations a lower priority, the low_priority_updates server system variable can be set to ON. The option is available on both the global and session levels, and it can be set at startup or via the SET statement.

When too many table locks have been set by write statements, some pending SELECTs are executed. The maximum number of write locks that can be acquired before this happens is determined by the max_write_lock_count server system variable, which is dynamic.

If write statements have a higher priority (default), the priority of individual write statements (INSERT, REPLACE, UPDATE, DELETE) can be changed via the LOW_PRIORITY attribute, and the priority of a SELECT statement can be raised via the HIGH_PRIORITY attribute. Also, LOCK TABLES supports a LOW_PRIORITY attribute for WRITE locks.

If read statements have a higher priority, the priority of an INSERT can be changed via the HIGH_PRIORITY attribute. However, the priority of other write statements cannot be raised individually.

The use of LOW_PRIORITY or HIGH_PRIORITY for an INSERT prevents Concurrent Inserts from being used.

See Also

GROUP BY

Use the GROUP BY clause in a SELECT statement to group rows together that have the same value in one or more column, or the same computed value using expressions with any functions and operators except grouping functions. When you use a GROUP BY clause, you will get a single result row for each group of rows that have the same value for the expression given in GROUP BY.

When grouping rows, grouping values are compared as if by the = operator. For string values, the = operator ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use.

You can use any of the grouping functions in your select expression. Their values will be calculated based on all the rows that have been grouped together for each result row. If you select a non-grouped column or a value computed from a non-grouped column, it is undefined which row the returned value is taken from. This is not permitted if the ONLY_FULL_GROUP_BY SQL_MODE is used.

You can use multiple expressions in the GROUP BY clause, separated by commas. Rows are grouped together if they match on each of the expressions.

You can also use a single integer as the grouping expression. If you use an integer n, the results will be grouped by the nth column in the select expression.

The WHERE clause is applied before the GROUP BY clause. It filters non-aggregated rows before the rows are grouped together. To filter grouped rows based on aggregate values, use the HAVING clause. The HAVING clause takes any expression and evaluates it as a boolean, just like the WHERE clause. You can use grouping functions in the HAVING clause. As with the select expression, if you reference non-grouped columns in the HAVING clause, the behavior is undefined.

By default, if a GROUP BY clause is present, the rows in the output will be sorted by the expressions used in the GROUP BY. You can also specify ASC or DESC (ascending, descending) after those expressions, like in ORDER BY. The default is ASC.

If you want the rows to be sorted by another field, you can add an explicit ORDER BY. If you don't want the result to be ordered, you can add ORDER BY NULL.

WITH ROLLUP

The WITH ROLLUP modifer adds extra rows to the resultset that represent super-aggregate summaries. For a full description with examples, see SELECT WITH ROLLUP.

GROUP BY Examples

Consider the following table that records how many times each user has played and won a game:

CREATE TABLE plays (name VARCHAR(16), plays INT, wins INT);
INSERT INTO plays VALUES 
  ("John", 20, 5), 
  ("Robert", 22, 8), 
  ("Wanda", 32, 8), 
  ("Susan", 17, 3);

Get a list of win counts along with a count:

SELECT wins, COUNT(*) FROM plays GROUP BY wins;
+------+----------+
| wins | COUNT(*) |
+------+----------+
|    3 |        1 |
|    5 |        1 |
|    8 |        2 |
+------+----------+
3 rows in set (0.00 sec)

The GROUP BY expression can be a computed value, and can refer back to an identifer specified with AS. Get a list of win averages along with a count:

SELECT (wins / plays) AS winavg, COUNT(*) FROM plays GROUP BY winavg;
+--------+----------+
| winavg | COUNT(*) |
+--------+----------+
| 0.1765 |        1 |
| 0.2500 |        2 |
| 0.3636 |        1 |
+--------+----------+
3 rows in set (0.00 sec)

You can use any grouping function in the select expression. For each win average as above, get a list of the average play count taken to get that average:

SELECT (wins / plays) AS winavg, AVG(plays) FROM plays 
  GROUP BY winavg;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.1765 |    17.0000 |
| 0.2500 |    26.0000 |
| 0.3636 |    22.0000 |
+--------+------------+
3 rows in set (0.00 sec)

You can filter on aggregate information using the HAVING clause. The HAVING clause is applied after GROUP BY and allows you to filter on aggregate data that is not available to the WHERE clause. Restrict the above example to results that involve an average number of plays over 20:

SELECT (wins / plays) AS winavg, AVG(plays) FROM plays 
  GROUP BY winavg HAVING AVG(plays) > 20;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.2500 |    26.0000 |
| 0.3636 |    22.0000 |
+--------+------------+
2 rows in set (0.00 sec)

See Also

INSERT - Default & Duplicate Values

Default Values

If the SQL_MODE contains STRICT_TRANS_TABLES and you are inserting into a transactional table (like InnoDB), or if the SQL_MODE contains STRICT_ALL_TABLES, all NOT NULL columns which does not have a DEFAULT value (and is not AUTO_INCREMENT) must be explicitly referenced in INSERT statements. If not, an error like this is produced:

ERROR 1364 (HY000): Field 'col' doesn't have a default value

In all other cases, if a NOT NULL column without a DEFAULT value is not referenced, an empty value will be inserted (for example, 0 for INTEGER columns and '' for CHAR columns). See NULL Values in MariaDB:Inserting for examples.

If a NOT NULL column having a DEFAULT value is not referenced, NULL will be inserted.

If a NULL column having a DEFAULT value is not referenced, its default value will be inserted. It is also possible to explicitly assign the default value using the DEFAULT keyword or the DEFAULT() function.

If the DEFAULT keyword is used but the column does not have a DEFAULT value, an error like this is produced:

ERROR 1364 (HY000): Field 'col' doesn't have a default value

Duplicate Values

By default, if you try to insert a duplicate row and there is a UNIQUE index, INSERT stops and an error like this is produced:

ERROR 1062 (23000): Duplicate entry 'dup_value' for key 'col'

To handle duplicates you can use the IGNORE clause, INSERT ON DUPLICATE KEY UPDATE or the REPLACE statement. Note that the IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

See Also

INSERT

Syntax

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
 [ ON DUPLICATE KEY UPDATE
   col=expr
     [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

The INSERT statement is used to insert new rows into an existing table. The INSERT ... VALUES and INSERT ... SET forms of the statement insert rows based on explicitly specified values. The INSERT ... SELECT form inserts rows selected from another table or tables. INSERT ... SELECT is discussed further in the INSERT ... SELECT article.

The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use INSERT ... SELECT to copy rows between different databases.

The PARTITION clause can be used in both the INSERT and the SELECT part. See Partition Pruning and Selection for details.

MariaDB starting with 10.5

The RETURNING clause was introduced in MariaDB 10.5.

The columns list is optional. It specifies which values are explicitly inserted, and in which order. If this clause is not specified, all values must be explicitly specified, in the same order they are listed in the table definition.

The list of value follow the VALUES or VALUE keyword (which are interchangeable, regardless how much values you want to insert), and is wrapped by parenthesis. The values must be listed in the same order as the columns list. It is possible to specify more than one list to insert more than one rows with a single statement. If many rows are inserted, this is a speed optimization.

For one-row statements, the SET clause may be more simple, because you don't need to remember the columns order. All values are specified in the form col = expr.

Values can also be specified in the form of a SQL expression or subquery. However, the subquery cannot access the same table that is named in the INTO clause.

If you use the LOW_PRIORITY keyword, execution of the INSERT is delayed until no other clients are reading from the table. If you use the HIGH_PRIORITY keyword, the statement has the same priority as SELECTs. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). However, if one of these keywords is specified, concurrent inserts cannot be used. See HIGH_PRIORITY and LOW_PRIORITY clauses for details.

INSERT DELAYED

For more details on the DELAYED option, see INSERT DELAYED.

HIGH PRIORITY and LOW PRIORITY

See HIGH_PRIORITY and LOW_PRIORITY.

Defaults and Duplicate Values

See INSERT - Default & Duplicate Values for details..

INSERT IGNORE

See INSERT IGNORE.

INSERT ON DUPLICATE KEY UPDATE

See INSERT ON DUPLICATE KEY UPDATE.

Examples

Specifying the column names:

INSERT INTO person (first_name, last_name) VALUES ('John', 'Doe');

Inserting more than 1 row at a time:

INSERT INTO tbl_name VALUES (1, "row 1"), (2, "row 2");

Using the SET clause:

INSERT INTO person SET first_name = 'John', last_name = 'Doe';

SELECTing from another table:

INSERT INTO contractor SELECT * FROM person WHERE status = 'c';

See INSERT ON DUPLICATE KEY UPDATE and INSERT IGNORE for further examples.

INSERT ... RETURNING

INSERT ... RETURNING returns a resultset of the inserted rows.

This returns the listed columns for all the rows that are inserted, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple INSERT statement

INSERT INTO t2 VALUES (1,'Dog'),(2,'Lion'),(3,'Tiger'),(4,'Leopard') 
RETURNING id2,id2+id2,id2&id2,id2||id2;
+-----+---------+---------+----------+
| id2 | id2+id2 | id2&id2 | id2||id2 |
+-----+---------+---------+----------+
|   1 |       2 |       1 |        1 |
|   2 |       4 |       2 |        1 |
|   3 |       6 |       3 |        1 |
|   4 |       8 |       4 |        1 |
+-----+---------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
       RETURN (SELECT arg+arg);
    END|

DELIMITER ;

PREPARE stmt FROM "INSERT INTO t1 SET id1=1, animal1='Bear' RETURNING f(id1), UPPER(animal1)";

EXECUTE stmt;
+---------+----------------+
| f(id1)  | UPPER(animal1) |
+---------+----------------+
|       2 | BEAR           |
+---------+----------------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used.

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values, and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used or it can be used in INSERT...SELECT...RETURNING if the table in the RETURNING clause is not the same as the INSERT table.

See Also

INSERT IGNORE

Ignoring Errors

Normally INSERT stops and rolls back when it encounters an error.

By using the IGNORE keyword all errors are converted to warnings, which will not stop inserts of additional rows.

The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

Prior to MySQL and MariaDB 5.5.28, no warnings were issued for duplicate key errors when using IGNORE. You can get the old behavior if you set OLD_MODE to NO_DUP_KEY_WARNINGS_WITH_IGNORE.

Examples

CREATE TABLE t1 (x INT UNIQUE);

INSERT INTO t1 VALUES(1),(2);

INSERT INTO t1 VALUES(2),(3);
ERROR 1062 (23000): Duplicate entry '2' for key 'x'
SELECT * FROM t1;
+------+
| x    |
+------+
|    1 |
|    2 |
+------+
2 rows in set (0.00 sec)

INSERT IGNORE INTO t1 VALUES(2),(3);
Query OK, 1 row affected, 1 warning (0.04 sec)

SHOW WARNINGS;
+---------+------+---------------------------------+
| Level   | Code | Message                         |
+---------+------+---------------------------------+
| Warning | 1062 | Duplicate entry '2' for key 'x' |
+---------+------+---------------------------------+

SELECT * FROM t1;
+------+
| x    |
+------+
|    1 |
|    2 |
|    3 |
+------+

See INSERT ON DUPLICATE KEY UPDATE for further examples using that syntax.

See Also

INSERT DELAYED

Syntax

INSERT DELAYED ...

Description

The DELAYED option for the INSERT statement is a MariaDB/MySQL extension to standard SQL that is very useful if you have clients that cannot or need not wait for the INSERT to complete. This is a common situation when you use MariaDB for logging and you also periodically run SELECT and UPDATE statements that take a long time to complete.

When a client uses INSERT DELAYED, it gets an okay from the server at once, and the row is queued to be inserted when the table is not in use by any other thread.

Another major benefit of using INSERT DELAYED is that inserts from many clients are bundled together and written in one block. This is much faster than performing many separate inserts.

Note that INSERT DELAYED is slower than a normal INSERT if the table is not otherwise in use. There is also the additional overhead for the server to handle a separate thread for each table for which there are delayed rows. This means that you should use INSERT DELAYED only when you are really sure that you need it.

The queued rows are held only in memory until they are inserted into the table. This means that if you terminate mysqld forcibly (for example, with kill -9) or if mysqld dies unexpectedly, any queued rows that have not been written to disk are lost.

The number of concurrent INSERT DELAYED threads is limited by the max_delayed_threads server system variables. If it is set to 0, INSERT DELAYED is disabled. The session value can be equal to the global value, or 0 to disable this statement for the current session. If this limit has been reached, the DELAYED clause will be silently ignore for subsequent statements (no error will be produced).

Limitations

There are some limitations on the use of DELAYED:

  • INSERT DELAYED works only with MyISAM, MEMORY, ARCHIVE, and BLACKHOLE tables. If you execute INSERT DELAYED with another storage engine, you will get an error like this: ERROR 1616 (HY000): DELAYED option not supported for table 'tab_name'
  • For MyISAM tables, if there are no free blocks in the middle of the data file, concurrent SELECT and INSERT statements are supported. Under these circumstances, you very seldom need to use INSERT DELAYED with MyISAM.
  • INSERT DELAYED should be used only for INSERT statements that specify value lists. The server ignores DELAYED for INSERT ... SELECT or INSERT ... ON DUPLICATE KEY UPDATE statements.
  • Because the INSERT DELAYED statement returns immediately, before the rows are inserted, you cannot use LAST_INSERT_ID() to get the AUTO_INCREMENT value that the statement might generate.
  • DELAYED rows are not visible to SELECT statements until they actually have been inserted.
  • After INSERT DELAYED, ROW_COUNT() returns the number of the rows you tried to insert, not the number of the successful writes.
  • DELAYED is ignored on slave replication servers, so that INSERT DELAYED is treated as a normal INSERT on slaves. This is because DELAYED could cause the slave to have different data than the master. INSERT DELAYED statements are not safe for replication.
  • Pending INSERT DELAYED statements are lost if a table is write locked and ALTER TABLE is used to modify the table structure.
  • INSERT DELAYED is not supported for views. If you try, you will get an error like this: ERROR 1347 (HY000): 'view_name' is not BASE TABLE
  • INSERT DELAYED is not supported for partitioned tables.
  • INSERT DELAYED is not supported within stored programs.
  • INSERT DELAYED does not work with triggers.
  • INSERT DELAYED does not work if there is a check constraint in place.
  • INSERT DELAYED does not work if skip-new mode is active.

See Also

INSERT SELECT

Syntax

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [(col_name,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

Description

With INSERT ... SELECT, you can quickly insert many rows into a table from one or more other tables. For example:

INSERT INTO tbl_temp2 (fld_id)
  SELECT tbl_temp1.fld_order_id
  FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;

tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers). This allows to copy rows between different databases.

If the new table has a primary key or UNIQUE indexes, you can use IGNORE to handle duplicate key errors during the query. The newer values will not be inserted if an identical value already exists.

REPLACE can be used instead of INSERT to prevent duplicates on UNIQUE indexes by deleting old values. In that case, ON DUPLICATE KEY UPDATE cannot be used.

INSERT ... SELECT works for tables which already exist. To create a table for a given resultset, you can use CREATE TABLE ... SELECT.

See Also

INTERSECT

MariaDB starting with 10.3.0

INTERSECT was introduced in MariaDB 10.3.0.

The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation.

Syntax

SELECT ...
(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Description

MariaDB has supported INTERSECT (as well as EXCEPT) in addition to UNION since MariaDB 10.3.

All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION.

INTERSECT implicitly supposes a DISTINCT operation.

The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation.

INTERSECT has higher precedence than UNION and EXCEPT (unless running running in Oracle mode, in which case all three have the same precedence). If possible it will be executed linearly but if not it will be translated to a subquery in the FROM clause:

(select a,b from t1)
union
(select c,d from t2)
intersect
(select e,f from t3)
union
(select 4,4);

will be translated to:

(select a,b from t1)
union
select c,d from
  ((select c,d from t2)
   intersect
   (select e,f from t3)) dummy_subselect
union
(select 4,4)



MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

MariaDB starting with 10.5.0

ALL/DISTINCT

INTERSECT ALL and INTERSECT DISTINCT were introduced in MariaDB 10.5.0. The ALL operator leaves duplicates intact, while the DISTINCT operator removes duplicates. DISTINCT is the default behavior if neither operator is supplied, and the only behavior prior to MariaDB 10.5.

Examples

Show customers which are employees:

(SELECT e_name AS name, email FROM employees)
INTERSECT
(SELECT c_name AS name, email FROM customers);

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3);
+------+
| a    |
+------+
|    1 |
|    6 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    6 |
+------+

See Also

INSERT ON DUPLICATE KEY UPDATE

Syntax

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
  [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
  {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
  [ ON DUPLICATE KEY UPDATE
    col=expr
      [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

Description

INSERT ... ON DUPLICATE KEY UPDATE is a MariaDB/MySQL extension to the INSERT statement that, if it finds a duplicate unique or primary key, will instead perform an UPDATE.

The row/s affected value is reported as 1 if a row is inserted, and 2 if a row is updated, unless the API's CLIENT_FOUND_ROWS flag is set.

If more than one unique index is matched, only the first is updated. It is not recommended to use this statement on tables with more than one unique index.

If the table has an AUTO_INCREMENT primary key and the statement inserts or updates a row, the LAST_INSERT_ID() function returns its AUTO_INCREMENT value.

The VALUES() function can only be used in a ON DUPLICATE KEY UPDATE clause and has no meaning in any other context. It returns the column values from the INSERT portion of the statement. This function is particularly useful for multi-rows inserts.

The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

MariaDB starting with 10.0

The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details.

This statement activates INSERT and UPDATE triggers. See Trigger Overview for details.

See also a similar statement, REPLACE.

Examples

CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal VARCHAR(30));
INSERT INTO ins_duplicate VALUES (1,'Aardvark'), (2,'Cheetah'), (3,'Zebra');

If there is no existing key, the statement runs as a regular INSERT:

INSERT INTO ins_duplicate VALUES (4,'Gorilla') ON DUPLICATE KEY UPDATE animal='Gorilla';
Query OK, 1 row affected (0.07 sec)
SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Aardvark |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

A regular INSERT with a primary key value of 1 will fail, due to the existing key:

INSERT INTO ins_duplicate VALUES (1,'Antelope');
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

However, we can use an INSERT ON DUPLICATE KEY UPDATE instead:

INSERT INTO ins_duplicate VALUES (1,'Antelope') ON DUPLICATE KEY UPDATE animal='Antelope';
Query OK, 2 rows affected (0.09 sec)

Note that there are two rows reported as affected, but this refers only to the UPDATE.

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

Adding a second unique column:

ALTER TABLE ins_duplicate ADD id2 INT;
UPDATE ins_duplicate SET id2=id+10;
ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2);

Where two rows match the unique keys match, only the first is updated. This can be unsafe and is not recommended unless you are certain what you are doing. Note that the warning shown below appears in MariaDB 5.5 and before, but has been removed in MariaDB 10.0, as MariaDB now assumes that the keys are checked in order, as shown in SHOW CREATE TABLE.

INSERT INTO ins_duplicate VALUES (2,'Lion',13) ON DUPLICATE KEY UPDATE animal='Lion';
Query OK, 2 rows affected, 1 warning (0.06 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                                                  |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1592 | Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. INSERT... ON DUPLICATE KEY UPDATE  on a table with more than one UNIQUE KEY is unsafe |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

SELECT * FROM ins_duplicate;
+----+----------+------+
| id | animal   | id2  |
+----+----------+------+
|  1 | Antelope |   11 |
|  2 | Lion     |   12 |
|  3 | Zebra    |   13 |
|  4 | Gorilla  |   14 |
+----+----------+------+

Although the third row with an id of 3 has an id2 of 13, which also matched, it was not updated.

Changing id to an auto_increment field. If a new row is added, the auto_increment is moved forward. If the row is updated, it remains the same.

ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT;
ALTER TABLE ins_duplicate DROP id2;
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (2,'Leopard') ON DUPLICATE KEY UPDATE animal='Leopard';
Query OK, 2 rows affected (0.00 sec)

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (5,'Wild Dog') ON DUPLICATE KEY UPDATE animal='Wild Dog';
Query OK, 1 row affected (0.09 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Leopard  |
|  3 | Zebra    |
|  4 | Gorilla  |
|  5 | Wild Dog |
+----+----------+

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              6 |
+----------------+

Refering to column values from the INSERT portion of the statement:

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
    ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

See the VALUES() function for more.

See Also

JOIN Syntax

Description

MariaDB supports the following JOIN syntaxes for the table_references part of SELECT statements and multiple-table DELETE and UPDATE statements:

table_references:
    table_reference [, table_reference] ...

table_reference:
    table_factor
  | join_table

table_factor:
    tbl_name [PARTITION (partition_list)]
        [query_system_time_period_specification] [[AS] alias] [index_hint_list]
  | table_subquery [query_system_time_period_specification] [AS] alias
  | ( table_references )
  | { ON table_reference LEFT OUTER JOIN table_reference
        ON conditional_expr }

join_table:
    table_reference [INNER | CROSS] JOIN table_factor [join_condition]
  | table_reference STRAIGHT_JOIN table_factor
  | table_reference STRAIGHT_JOIN table_factor ON conditional_expr
  | table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN table_factor

join_condition:
    ON conditional_expr
  | USING (column_list)

query_system_time_period_specification:
    FOR SYSTEM_TIME AS OF point_in_time
  | FOR SYSTEM_TIME BETWEEN point_in_time AND point_in_time
  | FOR SYSTEM_TIME FROM point_in_time TO point_in_time
  | FOR SYSTEM_TIME ALL

point_in_time:
    [TIMESTAMP] expression
  | TRANSACTION expression

index_hint_list:
    index_hint [, index_hint] ...

index_hint:
    USE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])
  | IGNORE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
  | FORCE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)

index_list:
    index_name [, index_name] ...

A table reference is also known as a join expression.

Each table can also be specified as db_name.tabl_name. This allows to write queries which involve multiple databases. See Identifier Qualifiers for syntax details.

The syntax of table_factor is extended in comparison with the SQL Standard. The latter accepts only table_reference, not a list of them inside a pair of parentheses.

This is a conservative extension if we consider each comma in a list of table_reference items as equivalent to an inner join. For example:

SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
                 ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

is equivalent to:

SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
                 ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

In MariaDB, CROSS JOIN is a syntactic equivalent to INNER JOIN (they can replace each other). In standard SQL, they are not equivalent. INNER JOIN is used with an ON clause, CROSS JOIN is used otherwise.

In general, parentheses can be ignored in join expressions containing only inner join operations. MariaDB also supports nested joins (see http://dev.mysql.com/doc/refman/5.1/en/nested-join-optimization.html).

See System-versioned tables for more information about FOR SYSTEM_TIME syntax.

Index hints can be specified to affect how the MariaDB optimizer makes use of indexes. For more information, see How to force query plans.

Examples

SELECT left_tbl.*
  FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id = right_tbl.id
  WHERE right_tbl.id IS NULL;

LOAD XML

Syntax

LOAD XML [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
    [REPLACE | IGNORE]
    INTO TABLE [db_name.]tbl_name
    [CHARACTER SET charset_name]
    [ROWS IDENTIFIED BY '<tagname>']
    [IGNORE number {LINES | ROWS}]
    [(column_or_user_var,...)]
    [SET col_name = expr,...]

Description

The LOAD XML statement reads data from an XML file into a table. The file_name must be given as a literal string. The tagname in the optional ROWS IDENTIFIED BY clause must also be given as a literal string, and must be surrounded by angle brackets (< and >).

LOAD XML acts as the complement of running the mysql client in XML output mode (that is, starting the client with the --xml option). To write data from a table to an XML file, use a command such as the following one from the system shell:

shell> mysql --xml -e 'SELECT * FROM mytable' > file.xml

To read the file back into a table, use LOAD XML INFILE. By default, the <row> element is considered to be the equivalent of a database table row; this can be changed using the ROWS IDENTIFIED BY clause.

This statement supports three different XML formats:

  • Column names as attributes and column values as attribute values:
<row column1="value1" column2="value2" .../>
  • Column names as tags and column values as the content of these tags:
<row>
  <column1>value1</column1>
  <column2>value2</column2>
</row>
  • Column names are the name attributes of <field> tags, and values are the contents of these tags:
<row>
  <field name='column1'>value1</field>
  <field name='column2'>value2</field>
</row>

This is the format used by other tools, such as mysqldump.

All 3 formats can be used in the same XML file; the import routine automatically detects the format for each row and interprets it correctly. Tags are matched based on the tag or attribute name and the column name.

The following clauses work essentially the same way for LOAD XML as they do for LOAD DATA:

  • LOW_PRIORITY or CONCURRENT
  • LOCAL
  • REPLACE or IGNORE
  • CHARACTER SET
  • (column_or_user_var,...)
  • SET

See LOAD DATA for more information about these clauses.

The IGNORE number LINES or IGNORE number ROWS clause causes the first number rows in the XML file to be skipped. It is analogous to the LOAD DATA statement's IGNORE ... LINES clause.

If the LOW_PRIORITY keyword is used, insertions are delayed until no other clients are reading from the table. The CONCURRENT keyword allowes the use of concurrent inserts. These clauses cannot be specified together.

This statement activates INSERT triggers.

See also

LIMIT

Description

Use the LIMIT clause to restrict the number of returned rows. When you use a single integer n with LIMIT, the first n rows will be returned. Use the ORDER BY clause to control which rows come first. You can also select a number of rows after an offset using either of the following:

LIMIT offset, row_count
LIMIT row_count OFFSET offset

When you provide an offset m with a limit n, the first m rows will be ignored, and the following n rows will be returned.

Executing an UPDATE with the LIMIT clause is not safe for replication. LIMIT 0 is an exception to this rule (see MDEV-6170).

There is a LIMIT ROWS EXAMINED optimization which provides the means to terminate the execution of SELECT statements which examine too many rows, and thus use too many resources. See LIMIT ROWS EXAMINED.

Multi-Table Updates

MariaDB starting with 10.3.2

Until MariaDB 10.3.1, it was not possible to use LIMIT (or ORDER BY) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2.

GROUP_CONCAT

MariaDB starting with 10.3.2

Starting from MariaDB 10.3.3, it is possible to use LIMIT with GROUP_CONCAT().

Examples

CREATE TABLE members (name VARCHAR(20));
INSERT INTO members VALUES('Jagdish'),('Kenny'),('Rokurou'),('Immaculada');

SELECT * FROM members;
+------------+
| name       |
+------------+
| Jagdish    |
| Kenny      |
| Rokurou    |
| Immaculada |
+------------+

Select the first two names (no ordering specified):

SELECT * FROM members LIMIT 2;
+---------+
| name    |
+---------+
| Jagdish |
| Kenny   |
+---------+

All the names in alphabetical order:

SELECT * FROM members ORDER BY name;
+------------+
| name       |
+------------+
| Immaculada |
| Jagdish    |
| Kenny      |
| Rokurou    |
+------------+

The first two names, ordered alphabetically:

SELECT * FROM members ORDER BY name LIMIT 2;
+------------+
| name       |
+------------+
| Immaculada |
| Jagdish    |
+------------+

The third name, ordered alphabetically (the first name would be offset zero, so the third is offset two):

SELECT * FROM members ORDER BY name LIMIT 2,1;
+-------+
| name  |
+-------+
| Kenny |
+-------+

From MariaDB 10.3.2, LIMIT can be used in a multi-table update:

CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100);

CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);

UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 
  WHERE (warehouse.product_id = store.product_id AND store.product_id  >= 1) 
    ORDER BY store.product_id DESC LIMIT 2;

SELECT * FROM warehouse;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |  100 |
|          2 |  100 |
|          3 |   98 |
|          4 |   98 |
+------------+------+

SELECT * FROM store;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |    5 |
|          2 |    5 |
|          3 |    7 |
|          4 |    7 |
+------------+------+

From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT, so, for example, given the following table:

CREATE TABLE d (dd DATE, cc INT);

INSERT INTO d VALUES ('2017-01-01',1);
INSERT INTO d VALUES ('2017-01-02',2);
INSERT INTO d VALUES ('2017-01-04',3);

the following query:

SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) FROM d;
+----------------------------------------------------------------------------+
| SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) |
+----------------------------------------------------------------------------+
| 2017-01-04:3                                                               |
+----------------------------------------------------------------------------+

can be more simply rewritten as:

SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) FROM d;
+-------------------------------------------------------------+
| GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) |
+-------------------------------------------------------------+
| 2017-01-04:3                                                |
+-------------------------------------------------------------+

See Also

Non-Recursive Common Table Expressions Overview

Common Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. There are two kinds of CTEs: Non-Recursive, which this article covers; and Recursive.

MariaDB starting with 10.2.1

Common table expressions were introduced in MariaDB 10.2.1.

Non-Recursive CTEs

The WITH keyword signifies a CTE. It is given a name, followed by a body (the main query) as follows: cte_syntax

CTEs are similar to derived tables. For example

WITH engineers AS 
   ( SELECT * FROM employees
     WHERE dept = 'Engineering' )

SELECT * FROM engineers
WHERE ...
SELECT * FROM
   ( SELECT * FROM employees
     WHERE dept = 'Engineering' ) AS engineers
WHERE
...

A non-recursive CTE is basically a query-local VIEW. There are several advantages and caveats to them. The syntax is more readable than nested FROM (SELECT ...). A CTE can refer to another and it can be referenced from multiple places.

A CTE referencing Another CTE

Using this format makes for a more readable SQL than a nested FROM(SELECT ...) clause. Below is an example of this:

WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') ),
eu_engineers AS ( SELECT * FROM engineers WHERE country IN('NL',...) )
SELECT
...
FROM eu_engineers;

Multiple Uses of a CTE

This can be an 'anti-self join', for example:

WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') )

SELECT * FROM engineers E1
WHERE NOT EXISTS
   (SELECT 1 FROM engineers E2
    WHERE E2.country=E1.country
    AND E2.name <> E1.name );

Or, for year-over-year comparisons, for example:

WITH sales_product_year AS (
SELECT product, YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year )

SELECT *
FROM sales_product_year CUR,
sales_product_year PREV,
WHERE CUR.product=PREV.product 
AND  CUR.year=PREV.year + 1 
AND CUR.total_amt > PREV.total_amt

Another use is to compare individuals against their group. Below is an example of how this might be executed:

WITH sales_product_year AS (
SELECT product,
YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year
)

SELECT * 
FROM sales_product_year S1
WHERE
total_amt > 
    (SELECT 0.1 * SUM(total_amt)
     FROM sales_product_year S2
     WHERE S2.year = S1.year)

LOAD DATA INFILE

Syntax

LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
    [REPLACE | IGNORE]
    INTO TABLE tbl_name
    [CHARACTER SET charset_name]
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]
    [IGNORE number LINES]
    [(col_name_or_user_var,...)]
    [SET col_name = expr,...]

Description

LOAD DATA INFILE is unsafe for statement-based replication.

Reads rows from a text file into the designated table on the database at a very high speed. The file name must be given as a literal string.

Files are written to disk using the SELECT INTO OUTFILE statement. You can then read the files back into a table using the LOAD DATA INFILE statement. The FIELDS and LINES clauses are the same in both statements. These clauses are optional, but if both are specified then the FIELDS clause must precede LINES.

Executing this statement activates INSERT triggers.

One must have the FILE privilege to be able to execute LOAD DATA. This is the ensure the normal users will not attempt to read system files.

Note that MariaDB's systemd unit file restricts access to /home, /root, and /run/user by default. See Configuring access to home directories.

LOAD DATA LOCAL INFILE

When you execute the LOAD DATA INFILE statement, MariaDB Server attempts to read the input file from its own file system. In contrast, when you execute the LOAD DATA LOCAL INFILE statement, the client attempts to read the input file from its file system, and it sends the contents of the input file to the MariaDB Server. This allows you to load files from the client's local file system into the database.

In the event that you don't want to permit this operation (such as for security reasons), you can disable the LOAD DATA LOCAL INFILE statement on either the server or the client.

  • The LOAD DATA LOCAL INFILE statement can be disabled on the server by setting the local_infile system variable to 0.
  • The LOAD DATA LOCAL INFILE statement can be disabled on the client. If you are using MariaDB Connector/C, this can be done by unsetting the CLIENT_LOCAL_FILES capability flag with the mysql_real_connect function or by unsetting the MYSQL_OPT_LOCAL_INFILE option with mysql_optionsv function. If you are using a different client or client library, then see the documentation for your specific client or client library to determine how it handles the LOAD DATA LOCAL INFILE statement.

If the LOAD DATA LOCAL INFILE statement is disabled by either the server or the client and if the user attempts to execute it, then the server will cause the statement to fail with the following error message:

The used command is not allowed with this MariaDB version

Note that it is not entirely accurate to say that the MariaDB version does not support the command. It would be more accurate to say that the MariaDB configuration does not support the command. See MDEV-20500 for more information.

From MariaDB 10.5.2, the error message is more accurate:

The used command is not allowed because the MariaDB server or client 
  has disabled the local infile capability

REPLACE and IGNORE

In cases where you load data from a file into a table that already contains data and has a primary key, you may encounter issues where the statement attempts to insert a row with a primary key that already exists. When this happens, the statement fails with Error 1064, protecting the data already on the table. In cases where you want MariaDB to overwrite duplicates, use the REPLACE keyword.

The REPLACE keyword works like the REPLACE statement. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it replaces the table data. That is, in the event of a conflict, it assumes the file contains the desired row.

This operation can cause a degradation in load speed by a factor of 20 or more if the part that has already been loaded is larger than the capacity of the InnoDB Buffer Pool. This happens because it causes a lot of turnaround in the buffer pool.

Use the IGNORE keyword when you want to skip any rows that contain a conflicting primary key. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing primary key, it ignores the addition request and moves on to the next. That is, in the event of a conflict, it assumes the table contains the desired row.

Character-sets

When the statement opens the file, it attempts to read the contents using the default character-set, as defined by the character_set_database system variable.

In the cases where the file was written using a character-set other than the default, you can specify the character-set to use with the CHARACTER SET clause in the statement. It ignores character-sets specified by the SET NAMES statement and by the character_set_client system variable. Setting the CHARACTER SET clause to a value of binary indicates "no conversion."

The statement interprets all fields in the file as having the same character-set, regardless of the column data type. To properly interpret file contents, you must ensure that it was written with the correct character-set. If you write a data file with mysqldump -T or with the SELECT INTO OUTFILE statement with the mysql client, be sure to use the --default-character-set option, so that the output is written with the desired character-set.

When using mixed character sets, use the CHARACTER SET clause in both SELECT INTO OUTFILE and LOAD DATA INFILE to ensure that MariaDB correctly interprets the escape sequences.

The character_set_filesystem system variable controls the interpretation of the filename.

It is currently not possible to load data files that use the ucs2 character set.

Preprocessing Inputs

col_name_or_user_var can be a column name, or a user variable. In the case of a variable, the SET statement can be used to preprocess the value before loading into the table.

Priority and Concurrency

In storage engines that perform table-level locking (MyISAM, MEMORY and MERGE), using the LOW_PRIORITY keyword, MariaDB delays insertions until no other clients are reading from the table. Alternatively, when using the MyISAM storage engine, you can use the CONCURRENT keyword to perform concurrent insertion.

The LOW_PRIORITY and CONCURRENT keywords are mutually exclusive. They cannot be used in the same statement.

Progress Reporting

The LOAD DATA INFILE statement supports progress reporting. You may find this useful when dealing with long-running operations. Using another client you can issue a SHOW PROCESSLIST query to check the progress of the data load.

Using mariadb-import/mysqlimport

MariaDB ships with a separate utility for loading data from files: mariadb-import (or mysqlimport before MariaDB 10.5). It operates by sending LOAD DATA INFILE statements to the server.

Using mariadb-import/mysqlimport you can compress the file using the --compress option, to get better performance over slow networks, providing both the client and server support the compressed protocol. Use the --local option to load from the local file system.

Indexing

In cases where the storage engine supports ALTER TABLE... DISABLE KEYS statements (MyISAM and Aria), the LOAD DATA INFILE statement automatically disables indexes during the execution.

Examples

You have a file with this content (note the the separator is ',', not tab, which is the default):

2,2
3,3
4,4
5,5
6,8
CREATE TABLE t1 (a int, b int, c int, d int);
LOAD DATA LOCAL INFILE 
 '/tmp/loaddata7.dat' into table t1 fields terminated by ',' (a,b) set c=a+b;
SELECT * FROM t1;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    2 |    2 |    4 |
|    3 |    3 |    6 |
|    4 |    4 |    8 |
|    5 |    5 |   10 |
|    6 |    8 |   14 |
+------+------+------+

Another example, given the following data (the separator is a tab):

1       a
2       b

The value of the first column is doubled before loading:

LOAD DATA INFILE 'ld.txt' INTO TABLE ld (@i,v) SET i=@i*2;

SELECT * FROM ld;
+------+------+
| i    | v    |
+------+------+
|    2 | a    |
|    4 | b    |
+------+------+

See Also

ORDER BY

Description

Use the ORDER BY clause to order a resultset, such as that are returned from a SELECT statement. You can specify just a column or use any expression with functions. If you are using the GROUP BY clause, you can use grouping functions in ORDER BY. Ordering is done after grouping.

You can use multiple ordering expressions, separated by commas. Rows will be sorted by the first expression, then by the second expression if they have the same value for the first, and so on.

You can use the keywords ASC and DESC after each ordering expression to force that ordering to be ascending or descending, respectively. Ordering is ascending by default.

You can also use a single integer as the ordering expression. If you use an integer n, the results will be ordered by the nth column in the select expression.

When string values are compared, they are compared as if by the STRCMP function. STRCMP ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use.

Duplicated entries in the ORDER BY clause are removed.

ORDER BY can also be used to order the activities of a DELETE or UPDATE statement (usually with the LIMIT clause).

MariaDB starting with 10.3.2

Until MariaDB 10.3.1, it was not possible to use ORDER BY (or LIMIT) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2.

MariaDB starting with 10.5

From MariaDB 10.5, MariaDB allows packed sort keys and values of non-sorted fields in the sort buffer. This can make filesort temporary files much smaller when VARCHAR, CHAR or BLOBs are used, notably speeding up some ORDER BY sorts.

Examples

CREATE TABLE seq (i INT, x VARCHAR(1));
INSERT INTO seq VALUES (1,'a'), (2,'b'), (3,'b'), (4,'f'), (5,'e');

SELECT * FROM seq ORDER BY i;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | b    |
|    4 | f    |
|    5 | e    |
+------+------+

SELECT * FROM seq ORDER BY i DESC;
+------+------+
| i    | x    |
+------+------+
|    5 | e    |
|    4 | f    |
|    3 | b    |
|    2 | b    |
|    1 | a    |
+------+------+

SELECT * FROM seq ORDER BY x,i;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | b    |
|    5 | e    |
|    4 | f    |
+------+------+

ORDER BY in an UPDATE statement, in conjunction with LIMIT:

UPDATE seq SET x='z' WHERE x='b' ORDER BY i DESC LIMIT 1;

SELECT * FROM seq;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | z    |
|    4 | f    |
|    5 | e    |
+------+------+

From MariaDB 10.3.2, ORDER BY can be used in a multi-table update:

CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100);

CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);

UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 
  WHERE (warehouse.product_id = store.product_id AND store.product_id  >= 1) 
    ORDER BY store.product_id DESC LIMIT 2;

SELECT * FROM warehouse;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |  100 |
|          2 |  100 |
|          3 |   98 |
|          4 |   98 |
+------------+------+

SELECT * FROM store;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |    5 |
|          2 |    5 |
|          3 |    7 |
|          4 |    7 |
+------------+------+

See Also

Recursive Common Table Expressions Overview

MariaDB starting with 10.2.2

Recursive Common Table Expressions have been supported since MariaDB 10.2.2.

Common Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. CTEs first appeared in the SQL standard in 1999, and the first implementations began appearing in 2007.

There are two kinds of CTEs:

SQL is generally poor at recursive structures.

trees_and_graphs

CTEs permit a query to reference itself. A recursive CTE will repeatedly execute subsets of the data until it obtains the complete result set. This makes it particularly useful for handing hierarchical or tree-structured data. max_recursive_iterations avoids infinite loops.

Syntax example

WITH RECURSIVE signifies a recursive CTE. It is given a name, followed by a body (the main query) as follows:

rcte_syntax

cte_syntax

Computation

Given the following structure: rcte_computation

First execute the anchor part of the query: rcte1

Next, execute the recursive part of the query: rcte_computation_2

rcte_computation_2b

rcte_computation_3

rcte_computation_3b

rcte_computation_4

Summary so far

with recursive R as (
  select anchor_data
  union [all]
  select recursive_part
  from R, ...
)
select ...
  1. Compute anchor_data
  2. Compute recursive_part to get the new data
  3. if (new data is non-empty) goto 2;

CAST to avoid truncating data

As currently implemented by MariaDB and by the SQL Standard, data may be truncated if not correctly cast. It is necessary to CAST the column to the correct width if the CTE's recursive part produces wider values for a column than the CTE's nonrecursive part. Some other DBMS give an error in this situation, and MariaDB's behavior may change in future - see MDEV-12325. See the examples below.

Examples

Transitive closure - determining bus destinations

Sample data:

tc_1

CREATE TABLE bus_routes (origin varchar(50), dst varchar(50));
INSERT INTO bus_routes VALUES 
  ('New York', 'Boston'), 
  ('Boston', 'New York'), 
  ('New York', 'Washington'), 
  ('Washington', 'Boston'), 
  ('Washington', 'Raleigh');

Now, we want to return the bus destinations with New York as the origin:

WITH RECURSIVE bus_dst as ( 
    SELECT origin as dst FROM bus_routes WHERE origin='New York' 
  UNION
    SELECT bus_routes.dst FROM bus_routes JOIN bus_dst ON bus_dst.dst= bus_routes.origin 
) 
SELECT * FROM bus_dst;
+------------+
| dst        |
+------------+
| New York   |
| Boston     |
| Washington |
| Raleigh    |
+------------+

The above example is computed as follows:

First, the anchor data is calculated:

  • Starting from New York
  • Boston and Washington are added

Next, the recursive part:

  • Starting from Boston and then Washington
  • Raleigh is added
  • UNION excludes nodes that are already present.

Computing paths - determining bus routes

This time, we are trying to get bus routes such as “New York -> Washington -> Raleigh”.

Using the same sample data as the previous example:

WITH RECURSIVE paths (cur_path, cur_dest) AS (
    SELECT origin, origin FROM bus_routes WHERE origin='New York' 
  UNION
    SELECT CONCAT(paths.cur_path, ',', bus_routes.dst), bus_routes.dst 
     FROM paths
     JOIN bus_routes 
       ON paths.cur_dest = bus_routes.origin AND 
         NOT FIND_IN_SET(bus_routes.dst, paths.cur_path)
) 
SELECT * FROM paths;
+-----------------------------+------------+
| cur_path                    | cur_dest   |
+-----------------------------+------------+
| New York                    | New York   |
| New York,Boston             | Boston     |
| New York,Washington         | Washington |
| New York,Washington,Boston  | Boston     |
| New York,Washington,Raleigh | Raleigh    |
+-----------------------------+------------+

CAST to avoid data truncation

In the following example, data is truncated because the results are not specifically cast to a wide enough type:

WITH RECURSIVE tbl AS (
  SELECT NULL AS col
  UNION
  SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)
SELECT col FROM tbl
+------+
| col  |
+------+
| NULL |
|      |
+------+

Explicitly use CAST to overcome this:

WITH RECURSIVE tbl AS (
  SELECT CAST(NULL AS CHAR(50)) AS col
  UNION SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)  
SELECT * FROM tbl;
+---------------------+
| col                 |
+---------------------+
| NULL                |
| THIS NEVER SHOWS UP |
+---------------------+

SELECT INTO DUMPFILE

Syntax

SELECT ... INTO DUMPFILE 'file_path'

Description

SELECT ... INTO DUMPFILE is a SELECT clause which writes the resultset into a single unformatted row, without any separators, in a file. The results will not be returned to the client.

file_path can be an absolute path, or a relative path starting from the data directory. It can only be specified as a string literal, not as a variable. However, the statement can be dynamically composed and executed as a prepared statement to work around this limitation.

This statement is binary-safe and so is particularly useful for writing BLOB values to file. It can be used, for example, to copy an image or an audio document from the database to a file. SELECT ... INTO FILE can be used to save a text file.

The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory.

Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings.

Example

SELECT _utf8'Hello world!' INTO DUMPFILE '/tmp/world';

SELECT LOAD_FILE('/tmp/world') AS world;
+--------------+
| world        |
+--------------+
| Hello world! |
+--------------+

See Also

SELECT

Syntax

SELECT [ALL | DISTINCT | DISTINCTROW] [HIGH_PRIORITY] [STRAIGHT_JOIN] [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT] [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS] select_expr [, select_expr ...] [ FROM table_references [WHERE where_condition] [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]] [HAVING where_condition] [ORDER BY {col_name | expr | position} [ASC | DESC], ...] [LIMIT {[offset,] row_count | row_count OFFSET offset [ROWS EXAMINED rows_limit] } | [OFFSET start { ROW | ROWS }] [FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } { ONLY | WITH TIES }] ] procedure|[PROCEDURE procedure_name(argument_list)] [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] [export_options] | INTO DUMPFILE 'file_name' | INTO var_name [, var_name] ] [FOR UPDATE lock_option | LOCK IN SHARE MODE lock_option]

export_options: [{FIELDS | COLUMNS} [TERMINATED BY 'string'] [[OPTIONALLY] ENCLOSED BY 'char'] [ESCAPED BY 'char'] ] [LINES [STARTING BY 'string'] [TERMINATED BY 'string'] ]

lock_option: [WAIT n | NOWAIT | SKIP LOCKED]

Description

SELECT is used to retrieve rows selected from one or more tables, and can include UNION statements and subqueries.

  • Each select_expr expression indicates a column or data that you want to retrieve. You must have at least one select expression. See Select Expressions below.
  • The FROM clause indicates the table or tables from which to retrieve rows. Use either a single table name or a JOIN expression. See JOIN for details. If no table is involved, FROM DUAL can be specified.
  • Each table can also be specified as db_name.tabl_name. Each column can also be specified as tbl_name.col_name or even db_name.tbl_name.col_name. This allows one to write queries which involve multiple databases. See Identifier Qualifiers for syntax details.
  • The WHERE clause, if given, indicates the condition or conditions that rows must satisfy to be selected. where_condition is an expression that evaluates to true for each row to be selected. The statement selects all rows if there is no WHERE clause.
  • Use the ORDER BY clause to order the results.
  • Use the LIMIT clause allows you to restrict the results to only a certain number of rows, optionally with an offset.
  • Use the GROUP BY and HAVING clauses to group rows together when they have columns or computed values in common.

SELECT can also be used to retrieve rows computed without reference to any table.

Select Expressions

A SELECT statement must contain one or more select expressions, separated by commas. Each select expression can be one of the following:

  • The name of a column.
  • Any expression using functions and operators.
  • * to select all columns from all tables in the FROM clause.
  • tbl_name.* to select all columns from just the table tbl_name.

When specifying a column, you can either use just the column name or qualify the column name with the name of the table using tbl_name.col_name. The qualified form is useful if you are joining multiple tables in the FROM clause. If you do not qualify the column names when selecting from multiple tables, MariaDB will try to find the column in each table. It is an error if that column name exists in multiple tables.

You can quote column names using backticks. If you are qualifying column names with table names, quote each part separately as `tbl_name`.`col_name`.

If you use any grouping functions in any of the select expressions, all rows in your results will be implicitly grouped, as if you had used GROUP BY NULL.

DISTINCT

A query may produce some identical rows. By default, all rows are retrieved, even when their values are the same. To explicitly specify that you want to retrieve identical rows, use the ALL option. If you want duplicates to be removed from the resultset, use the DISTINCT option. DISTINCTROW is a synonym for DISTINCT. See also COUNT DISTINCT and SELECT UNIQUE in Oracle mode.

INTO

The INTO clause is used to specify that the query results should be written to a file or variable.

The reverse of SELECT INTO OUTFILE is LOAD DATA.

LIMIT

Restricts the number of returned rows. See LIMIT and LIMIT ROWS EXAMINED for details.

LOCK IN SHARE MODE/FOR UPDATE

See LOCK IN SHARE MODE and FOR UPDATE for details on the respective locking clauses.

OFFSET ... FETCH

MariaDB starting with 10.6

See SELECT ... OFFSET ... FETCH.

ORDER BY

Order a resultset. See ORDER BY for details.

PARTITION

Specifies to the optimizer which partitions are relevant for the query. Other partitions will not be read. See Partition Pruning and Selection for details.

PROCEDURE

Passes the whole result set to a C Procedure. See PROCEDURE and PROCEDURE ANALYSE (the only built-in procedure not requiring the server to be recompiled).

SKIP LOCKED

MariaDB starting with 10.6

The SKIP LOCKED clause was introduced in MariaDB 10.6.0.

This causes those rows that couldn't be locked (LOCK IN SHARE MODE or FOR UPDATE) to be excluded from the result set. An explicit NOWAIT is implied here. This is only implemented on InnoDB tables and ignored otherwise.

SQL_CALC_FOUND_ROWS

When SQL_CALC_FOUND_ROWS is used, then MariaDB will calculate how many rows would have been in the result, if there would be no LIMIT clause. The result can be found by calling the function FOUND_ROWS() in your next sql statement.


max_statement_time clause

By using max_statement_time in conjunction with SET STATEMENT, it is possible to limit the execution time of individual queries. For example:

SET STATEMENT max_statement_time=100 FOR 
  SELECT field1 FROM table_name ORDER BY field1;

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Examples

SELECT f1,f2 FROM t1 WHERE (f3<=10) AND (f4='y');

See Getting Data from MariaDB (Beginner tutorial), or the various sub-articles, for more examples.

See Also

SELECT INTO OUTFILE

Syntax

SELECT ... INTO OUTFILE 'file_name'
        [CHARACTER SET charset_name]
        [export_options]

export_options:
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]

Description

SELECT INTO OUTFILE writes the resulting rows to a file, and allows the use of column and row terminators to specify a particular output format. The default is to terminate fields with tabs (\t) and lines with newlines (\n).

The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory.

The LOAD DATA INFILE statement complements SELECT INTO OUTFILE.

Character-sets

The CHARACTER SET clause specifies the character set in which the results are to be written. Without the clause, no conversion takes place (the binary character set). In this case, if there are multiple character sets, the output will contain these too, and may not easily be able to be reloaded.

In cases where you have two servers using different character-sets, using SELECT INTO OUTFILE to transfer data from one to the other can have unexpected results. To ensure that MariaDB correctly interprets the escape sequences, use the CHARACTER SET clause on both the SELECT INTO OUTFILE statement and the subsequent LOAD DATA INFILE statement.

Example

The following example produces a file in the CSV format:

SELECT customer_id, firstname, surname INTO OUTFILE '/exportdata/customers.txt'
  FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
  LINES TERMINATED BY '\n'
  FROM customers;

See Also

SELECT WITH ROLLUP

Syntax

See SELECT for the full syntax.

Description

The WITH ROLLUP modifier adds extra rows to the resultset that represent super-aggregate summaries. The super-aggregated column is represented by a NULL value. Multiple aggregates over different columns will be added if there are multiple GROUP BY columns.

The LIMIT clause can be used at the same time, and is applied after the WITH ROLLUP rows have been added.

WITH ROLLUP cannot be used with ORDER BY. Some sorting is still possible by using ASC or DESC clauses with the GROUP BY column, although the super-aggregate rows will always be added last.

Examples

These examples use the following sample table

CREATE TABLE booksales ( 
  country VARCHAR(35), genre ENUM('fiction','non-fiction'), year YEAR, sales INT);

INSERT INTO booksales VALUES
  ('Senegal','fiction',2014,12234), ('Senegal','fiction',2015,15647),
  ('Senegal','non-fiction',2014,64980), ('Senegal','non-fiction',2015,78901),
  ('Paraguay','fiction',2014,87970), ('Paraguay','fiction',2015,76940),
  ('Paraguay','non-fiction',2014,8760), ('Paraguay','non-fiction',2015,9030);

The addition of the WITH ROLLUP modifier in this example adds an extra row that aggregates both years:

SELECT year, SUM(sales) FROM booksales GROUP BY year;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
+------+------------+
2 rows in set (0.08 sec)

SELECT year, SUM(sales) FROM booksales GROUP BY year WITH ROLLUP;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
| NULL |     354462 |
+------+------------+

In the following example, each time the genre, the year or the country change, another super-aggregate row is added:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
+----------+------+-------------+------------+

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+

The LIMIT clause, applied after WITH ROLLUP:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP LIMIT 4;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
+----------+------+-------------+------------+

Sorting by year descending:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year DESC, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+

See Also

UNION

UNION is used to combine the results from multiple SELECT statements into a single result set.

Syntax

SELECT ...
UNION [ALL | DISTINCT] SELECT ...
[UNION [ALL | DISTINCT] SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Description

UNION is used to combine the results from multiple SELECT statements into a single result set.

The column names from the first SELECT statement are used as the column names for the results returned. Selected columns listed in corresponding positions of each SELECT statement should have the same data type. (For example, the first column selected by the first statement should have the same type as the first column selected by the other statements.)

If they don't, the type and length of the columns in the result take into account the values returned by all of the SELECTs, so there is no need for explicit casting. Note that currently this is not the case for recursive CTEs - see MDEV-12325.

Table names can be specified as db_name.tbl_name. This permits writing UNIONs which involve multiple databases. See Identifier Qualifiers for syntax details.

UNION queries cannot be used with aggregate functions.

EXCEPT and UNION have the same operation precedence and INTERSECT has a higher precedence, unless running in Oracle mode, in which case all three have the same precedence.

ALL/DISTINCT

The ALL keyword causes duplicate rows to be preserved. The DISTINCT keyword (the default if the keyword is omitted) causes duplicate rows to be removed by the results.

UNION ALL and UNION DISTINCT can both be present in a query. In this case, UNION DISTINCT will override any UNION ALLs to its left.

MariaDB starting with 10.1.1

Until MariaDB 10.1.1, all UNION ALL statements required the server to create a temporary table. Since MariaDB 10.1.1, the server can in most cases execute UNION ALL without creating a temporary table, improving performance (see MDEV-334).

ORDER BY and LIMIT

Individual SELECTs can contain their own ORDER BY and LIMIT clauses. In this case, the individual queries need to be wrapped between parentheses. However, this does not affect the order of the UNION, so they only are useful to limit the record read by one SELECT.

The UNION can have global ORDER BY and LIMIT clauses, which affect the whole resultset. If the columns retrieved by individual SELECT statements have an alias (AS), the ORDER BY must use that alias, not the real column names.

HIGH_PRIORITY

Specifying a query as HIGH_PRIORITY will not work inside a UNION. If applied to the first SELECT, it will be ignored. Applying to a later SELECT results in a syntax error:

ERROR 1234 (42000): Incorrect usage/placement of 'HIGH_PRIORITY'

SELECT ... INTO ...

Individual SELECTs cannot be written INTO DUMPFILE or INTO OUTFILE. If the last SELECT statement specifies INTO DUMPFILE or INTO OUTFILE, the entire result of the UNION will be written. Placing the clause after any other SELECT will result in a syntax error.

If the result is a single row, SELECT ... INTO @var_name can also be used.

MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

Examples

UNION between tables having different column names:

(SELECT e_name AS name, email FROM employees)
UNION
(SELECT c_name AS name, email FROM customers);

Specifying the UNION's global order and limiting total rows:

(SELECT name, email FROM employees)
UNION
(SELECT name, email FROM customers)
ORDER BY name LIMIT 10;

Adding a constant row:

(SELECT 'John Doe' AS name, 'john.doe@example.net' AS email)
UNION
(SELECT name, email FROM customers);

Differing types:

SELECT CAST('x' AS CHAR(1)) UNION SELECT REPEAT('y',4);
+----------------------+
| CAST('x' AS CHAR(1)) |
+----------------------+
| x                    |
| yyyy                 |
+----------------------+

Returning the results in order of each individual SELECT by use of a sort column:

(SELECT 1 AS sort_column, e_name AS name, email FROM employees)
UNION
(SELECT 2, c_name AS name, email FROM customers) ORDER BY sort_column;

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3);
+------+
| a    |
+------+
|    1 |
|    6 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    6 |
+------+

See Also

WITH

MariaDB starting with 10.2.1

Common Table Expressions were introduced in MariaDB 10.2.1.

Syntax

WITH [RECURSIVE] table_reference [(columns_list)] AS  (
  SELECT ...
)
[CYCLE cycle_column_list RESTRICT]
SELECT ...

Description

The WITH keyword signifies a Common Table Expression (CTE). It allows you to refer to a subquery expression many times in a query, as if having a temporary table that only exists for the duration of a query.

There are two kinds of CTEs:

You can use table_reference as any normal table in the external SELECT part. You can also use WITH in subqueries, as well as with EXPLAIN and SELECT.

Poorly-formed recursive CTEs can in theory cause infinite loops. The max_recursive_iterations system variable limits the number of recursions.

CYCLE ... RESTRICT

MariaDB starting with 10.5.2

The CYCLE clause enables CTE cycle detection, avoiding excessive or infinite loops, MariaDB supports a relaxed, non-standard grammar.

The SQL Standard permits a CYCLE clause, as follows:

WITH RECURSIVE ... (
  ...
)
CYCLE <cycle column list>
SET <cycle mark column> TO <cycle mark value> DEFAULT <non-cycle mark value>
USING <path column>

where all clauses are mandatory.

MariaDB does not support this, but from 10.5.2 permits a non-standard relaxed grammar, as follows:

WITH RECURSIVE ... (
  ...
)
CYCLE <cycle column list> RESTRICT

With the use of CYCLE ... RESTRICT it makes no difference whether the CTE uses UNION ALL or UNION DISTINCT anymore. UNION ALL means "all rows, but without cycles", which is exactly what the CYCLE clause enables. And UNION DISTINCT means all rows should be different, which, again, is what will happen — as uniqueness is enforced over a subset of columns, complete rows will automatically all be different.

Examples

Below is an example with the WITH at the top level:

WITH t AS (SELECT a FROM t1 WHERE b >= 'c') 
  SELECT * FROM t2, t WHERE t2.c = t.a;

The example below uses WITH in a subquery:

SELECT t1.a, t1.b FROM t1, t2
  WHERE t1.a > t2.c 
     AND t2.c IN(WITH t AS (SELECT * FROM t1 WHERE t1.a < 5)
                SELECT t2.c FROM t2, t WHERE t2.c = t.a);

Below is an example of a Recursive CTE:

WITH RECURSIVE ancestors AS 
 ( SELECT * FROM folks
   WHERE name="Alex"
   UNION
   SELECT f.*
   FROM folks AS f, ancestors AS a
   WHERE f.id = a.father OR f.id = a.mother )
SELECT * FROM ancestors;

Take the following structure, and data,

CREATE TABLE t1 (from_ int, to_ int);
INSERT INTO t1 VALUES (1,2), (1,100), (2,3), (3,4), (4,1);
SELECT * FROM t1;
+-------+------+
| from_ | to_  |
+-------+------+
|     1 |    2 |
|     1 |  100 |
|     2 |    3 |
|     3 |    4 |
|     4 |    1 |
+-------+------+

Given the above, the following query would theoretically result in an infinite loop due to the last record in t1 (note that max_recursive_iterations is set to 10 for the purposes of this example, to avoid the excessive number of cycles):

SET max_recursive_iterations=10;

WITH RECURSIVE cte (depth, from_, to_) AS ( 
  SELECT 0,1,1 UNION DISTINCT SELECT depth+1, t1.from_, t1.to_ 
    FROM t1, cte  WHERE t1.from_ = cte.to_ 
) 
SELECT * FROM cte;
+-------+-------+------+
| depth | from_ | to_  |
+-------+-------+------+
|     0 |     1 |    1 |
|     1 |     1 |    2 |
|     1 |     1 |  100 |
|     2 |     2 |    3 |
|     3 |     3 |    4 |
|     4 |     4 |    1 |
|     5 |     1 |    2 |
|     5 |     1 |  100 |
|     6 |     2 |    3 |
|     7 |     3 |    4 |
|     8 |     4 |    1 |
|     9 |     1 |    2 |
|     9 |     1 |  100 |
|    10 |     2 |    3 |
+-------+-------+------+

However, the CYCLE ... RESTRICT clause (from MariaDB 10.5.2) can overcome this:

WITH RECURSIVE cte (depth, from_, to_) AS ( 
  SELECT 0,1,1 UNION SELECT depth+1, t1.from_, t1.to_ 
    FROM t1, cte WHERE t1.from_ = cte.to_ 
) 
CYCLE from_, to_ RESTRICT 
SELECT * FROM cte;
+-------+-------+------+
| depth | from_ | to_  |
+-------+-------+------+
|     0 |     1 |    1 |
|     1 |     1 |    2 |
|     1 |     1 |  100 |
|     2 |     2 |    3 |
|     3 |     3 |    4 |
|     4 |     4 |    1 |
+-------+-------+------+

See Also

DESCRIBE

Syntax

{DESCRIBE | DESC} tbl_name [col_name | wild]

Description

DESCRIBE provides information about the columns in a table. It is a shortcut for SHOW COLUMNS FROM. These statements also display information for views.

col_name can be a column name, or a string containing the SQL "%" and "_" wildcard characters to obtain output only for the columns with names matching the string. There is no need to enclose the string within quotes unless it contains spaces or other special characters.

DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | YES  |     | NULL    |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+

The description for SHOW COLUMNS provides more information about the output columns.

See Also

CROSSES

Syntax

Crosses(g1,g2)

Description

Returns 1 if g1 spatially crosses g2. Returns NULL if g1 is a Polygon or a MultiPolygon, or if g2 is a Point or a MultiPoint. Otherwise, returns 0.

The term spatially crosses denotes a spatial relation between two given geometries that has the following properties:

  • The two geometries intersect
  • Their intersection results in a geometry that has a dimension that is one less than the maximum dimension of the two given geometries
  • Their intersection is not equal to either of the two given geometries

CROSSES() is based on the original MySQL implementation, and uses object bounding rectangles, while ST_CROSSES() uses object shapes.

ST_CONTAINS

Syntax

ST_CONTAINS(g1,g2)

Description

Returns 1 or 0 to indicate whether a geometry g1 completely contains geometry g2.

ST_CONTAINS() uses object shapes, while CONTAINS(), based on the original MySQL implementation, uses object bounding rectangles.

ST_CONTAINS tests the opposite relationship to ST_WITHIN().

Examples

SET @g1 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))');

SET @g2 = ST_GEOMFROMTEXT('POINT(174 149)');

SELECT ST_CONTAINS(@g1,@g2);
+----------------------+
| ST_CONTAINS(@g1,@g2) |
+----------------------+
|                    1 |
+----------------------+

SET @g2 = ST_GEOMFROMTEXT('POINT(175 151)');

SELECT ST_CONTAINS(@g1,@g2);
+----------------------+
| ST_CONTAINS(@g1,@g2) |
+----------------------+
|                    0 |
+----------------------+

ST_CROSSES

Syntax

ST_CROSSES(g1,g2)

Description

Returns 1 if geometry g1 spatially crosses geometry g2. Returns NULL if g1 is a Polygon or a MultiPolygon, or if g2 is a Point or a MultiPoint. Otherwise, returns 0.

The term spatially crosses denotes a spatial relation between two given geometries that has the following properties:

  • The two geometries intersect
  • Their intersection results in a geometry that has a dimension that is one less than the maximum dimension of the two given geometries
  • Their intersection is not equal to either of the two given geometries

ST_CROSSES() uses object shapes, while CROSSES(), based on the original MySQL implementation, uses object bounding rectangles.

Examples

SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)');

SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))');

SELECT ST_CROSSES(@g1,@g2);
+---------------------+
| ST_CROSSES(@g1,@g2) |
+---------------------+
|                   1 |
+---------------------+

SET @g1 = ST_GEOMFROMTEXT('LINESTRING(176 149, 176 151)');

SELECT ST_CROSSES(@g1,@g2);
+---------------------+
| ST_CROSSES(@g1,@g2) |
+---------------------+
|                   0 |
+---------------------+

ST_DISJOINT

Syntax

ST_DISJOINT(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 is spatially disjoint from (does not intersect with) geometry g2.

ST_DISJOINT() uses object shapes, while DISJOINT(), based on the original MySQL implementation, uses object bounding rectangles.

ST_DISJOINT() tests the opposite relationship to ST_INTERSECTS().

Examples

SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');

SELECT ST_DISJOINT(@g1,@g2);
+----------------------+
| ST_DISJOINT(@g1,@g2) |
+----------------------+
|                    1 |
+----------------------+

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)');

SELECT ST_DISJOINT(@g1,@g2);
+----------------------+
| ST_DISJOINT(@g1,@g2) |
+----------------------+
|                    0 |
+----------------------+

ST_EQUALS

Syntax

ST_EQUALS(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 is spatially equal to geometry g2.

ST_EQUALS() uses object shapes, while EQUALS(), based on the original MySQL implementation, uses object bounding rectangles.

Examples

SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(176 151, 174 149)');

SELECT ST_EQUALS(@g1,@g2);
+--------------------+
| ST_EQUALS(@g1,@g2) |
+--------------------+
|                  1 |
+--------------------+
SET @g1 = ST_GEOMFROMTEXT('POINT(0 2)');

SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)');

SELECT ST_EQUALS(@g1,@g2);
+--------------------+
| ST_EQUALS(@g1,@g2) |
+--------------------+
|                  0 |
+--------------------+

ST_INTERSECTS

Syntax

ST_INTERSECTS(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 spatially intersects geometry g2.

ST_INTERSECTS() uses object shapes, while INTERSECTS(), based on the original MySQL implementation, uses object bounding rectangles.

ST_INTERSECTS() tests the opposite relationship to ST_DISJOINT().

Examples

SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)');

SELECT ST_INTERSECTS(@g1,@g2);
+------------------------+
| ST_INTERSECTS(@g1,@g2) |
+------------------------+
|                      1 |
+------------------------+
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');

SELECT ST_INTERSECTS(@g1,@g2);
+------------------------+
| ST_INTERSECTS(@g1,@g2) |
+------------------------+
|                      0 |
+------------------------+

ST_TOUCHES

Syntax

ST_TOUCHES(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 spatially touches geometry g2. Two geometries spatially touch if the interiors of the geometries do not intersect, but the boundary of one of the geometries intersects either the boundary or the interior of the other.

ST_TOUCHES() uses object shapes, while TOUCHES(), based on the original MySQL implementation, uses object bounding rectangles.

Examples

SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)');

SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');

SELECT ST_TOUCHES(@g1,@g2);
+---------------------+
| ST_TOUCHES(@g1,@g2) |
+---------------------+
|                   1 |
+---------------------+

SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)');

SELECT ST_TOUCHES(@g1,@g2);
+---------------------+
| ST_TOUCHES(@g1,@g2) |
+---------------------+
|                   0 |
+---------------------+

ST_WITHIN

Syntax

ST_WITHIN(g1,g2)

Description

Returns 1 or 0 to indicate whether geometry g1 is spatially within geometry g2.

This tests the opposite relationship as ST_CONTAINS().

ST_WITHIN() uses object shapes, while WITHIN(), based on the original MySQL implementation, uses object bounding rectangles.

Examples

SET @g1 = ST_GEOMFROMTEXT('POINT(174 149)');

SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))');

SELECT ST_WITHIN(@g1,@g2);
+--------------------+
| ST_WITHIN(@g1,@g2) |
+--------------------+
|                  1 |
+--------------------+

SET @g1 = ST_GEOMFROMTEXT('POINT(176 151)');

SELECT ST_WITHIN(@g1,@g2);
+--------------------+
| ST_WITHIN(@g1,@g2) |
+--------------------+
|                  0 |
+--------------------+

WITHIN

Syntax

Within(g1,g2)

Description

Returns 1 or 0 to indicate whether g1 is spatially within g2. This tests the opposite relationship as Contains().

WITHIN() is based on the original MySQL implementation, and uses object bounding rectangles, while ST_WITHIN() uses object shapes.

Examples

SET @g1 = GEOMFROMTEXT('POINT(174 149)');
SET @g2 = GEOMFROMTEXT('POINT(176 151)');
SET @g3 = GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))');

SELECT within(@g1,@g3);
+-----------------+
| within(@g1,@g3) |
+-----------------+
|               1 |
+-----------------+

SELECT within(@g2,@g3);
+-----------------+
| within(@g2,@g3) |
+-----------------+
|               0 |
+-----------------+

ADDDATE

Syntax

ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days)

Description

When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD().

When invoked with the days form of the second argument, MariaDB treats it as an integer number of days to be added to expr.

Examples

SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_ADD('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2008-02-02                              |
+-----------------------------------------+

SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| ADDDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2008-02-02                             |
+----------------------------------------+
SELECT ADDDATE('2008-01-02', 31);
+---------------------------+
| ADDDATE('2008-01-02', 31) |
+---------------------------+
| 2008-02-02                |
+---------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d, ADDDATE(d, 10) from t1;
+---------------------+---------------------+
| d                   | ADDDATE(d, 10)      |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-02-09 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-25 06:42:51 |
| 2011-04-21 12:34:56 | 2011-05-01 12:34:56 |
| 2011-10-30 06:31:41 | 2011-11-09 06:31:41 |
| 2011-01-30 14:03:25 | 2011-02-09 14:03:25 |
| 2004-10-07 11:19:34 | 2004-10-17 11:19:34 |
+---------------------+---------------------+

SELECT d, ADDDATE(d, INTERVAL 10 HOUR) from t1;
+---------------------+------------------------------+
| d                   | ADDDATE(d, INTERVAL 10 HOUR) |
+---------------------+------------------------------+
| 2007-01-30 21:31:07 | 2007-01-31 07:31:07          |
| 1983-10-15 06:42:51 | 1983-10-15 16:42:51          |
| 2011-04-21 12:34:56 | 2011-04-21 22:34:56          |
| 2011-10-30 06:31:41 | 2011-10-30 16:31:41          |
| 2011-01-30 14:03:25 | 2011-01-31 00:03:25          |
| 2004-10-07 11:19:34 | 2004-10-07 21:19:34          |
+---------------------+------------------------------+

ADDTIME

Syntax

ADDTIME(expr1,expr2)

Description

ADDTIME() adds expr2 to expr1 and returns the result. expr1 is a time or datetime expression, and expr2 is a time expression.

Examples

SELECT ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002');
+---------------------------------------------------------+
| ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002') |
+---------------------------------------------------------+
| 2008-01-02 01:01:01.000001                              |
+---------------------------------------------------------+

SELECT ADDTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| ADDTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| 03:00:01.999997                               |
+-----------------------------------------------+

CONVERT_TZ

Syntax

CONVERT_TZ(dt,from_tz,to_tz)

Description

CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value.

In order to use named time zones, such as GMT, MET or Africa/Johannesburg, the time_zone tables must be loaded (see mysql_tzinfo_to_sql).

No conversion will take place if the value falls outside of the supported TIMESTAMP range ('1970-01-01 00:00:01' to '2038-01-19 05:14:07' UTC) when converted from from_tz to UTC.

This function returns NULL if the arguments are invalid (or named time zones have not been loaded).

See time zones for more information.

Examples

SELECT CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00') |
+-----------------------------------------------------+
| 2016-01-01 22:00:00                                 |
+-----------------------------------------------------+

Using named time zones (with the time zone tables loaded):

SELECT CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg');
+---------------------------------------------------------------+
| CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg') |
+---------------------------------------------------------------+
| 2016-01-01 14:00:00                                           |
+---------------------------------------------------------------+

The value is out of the TIMESTAMP range, so no conversion takes place:

SELECT CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00') |
+-----------------------------------------------------+
| 1969-12-31 22:00:00                                 |
+-----------------------------------------------------+

CURDATE

Syntax

CURDATE()
CURRENT_DATE
CURRENT_DATE()

Description

CURDATE returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

CURRENT_DATE and CURRENT_DATE() are synonyms.

Examples

SELECT CURDATE();
+------------+
| CURDATE()  |
+------------+
| 2019-03-05 |
+------------+

In a numeric context (note this is not performing date calculations):

SELECT CURDATE() +0;
+--------------+
| CURDATE() +0 |
+--------------+
|     20190305 |
+--------------+

Data calculation:

SELECT CURDATE() - INTERVAL 5 DAY;
+----------------------------+
| CURDATE() - INTERVAL 5 DAY |
+----------------------------+
| 2019-02-28                 |
+----------------------------+

DATEDIFF

Syntax

DATEDIFF(expr1,expr2)

Description

DATEDIFF() returns (expr1 expr2) expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

Examples

SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
+----------------------------------------------+
| DATEDIFF('2007-12-31 23:59:59','2007-12-30') |
+----------------------------------------------+
|                                            1 |
+----------------------------------------------+

SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
+----------------------------------------------+
| DATEDIFF('2010-11-30 23:59:59','2010-12-31') |
+----------------------------------------------+
|                                          -31 |
+----------------------------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT NOW();
+---------------------+
| NOW()               |
+---------------------+
| 2011-05-23 10:56:05 |
+---------------------+

SELECT d, DATEDIFF(NOW(),d) FROM t1;
+---------------------+-------------------+
| d                   | DATEDIFF(NOW(),d) |
+---------------------+-------------------+
| 2007-01-30 21:31:07 |              1574 |
| 1983-10-15 06:42:51 |             10082 |
| 2011-04-21 12:34:56 |                32 |
| 2011-10-30 06:31:41 |              -160 |
| 2011-01-30 14:03:25 |               113 |
| 2004-10-07 11:19:34 |              2419 |
+---------------------+-------------------+

DATE_ADD

Syntax

DATE_ADD(date,INTERVAL expr unit)

Description

Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units.

Examples

SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
+-------------------------------------------+
| '2008-12-31 23:59:59' + INTERVAL 1 SECOND |
+-------------------------------------------+
| 2009-01-01 00:00:00                       |
+-------------------------------------------+
SELECT INTERVAL 1 DAY + '2008-12-31';
+-------------------------------+
| INTERVAL 1 DAY + '2008-12-31' |
+-------------------------------+
| 2009-01-01                    |
+-------------------------------+
SELECT '2005-01-01' - INTERVAL 1 SECOND;
+----------------------------------+
| '2005-01-01' - INTERVAL 1 SECOND |
+----------------------------------+
| 2004-12-31 23:59:59              |
+----------------------------------+
SELECT DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND);
+----------------------------------------------------+
| DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND) |
+----------------------------------------------------+
| 2001-01-01 00:00:00                                |
+----------------------------------------------------+
SELECT DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY);
+-------------------------------------------------+
| DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY) |
+-------------------------------------------------+
| 2011-01-01 23:59:59                             |
+-------------------------------------------------+
SELECT DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND);
+---------------------------------------------------------------+
| DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND) |
+---------------------------------------------------------------+
| 2101-01-01 00:01:00                                           |
+---------------------------------------------------------------+
SELECT DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR);
+------------------------------------------------------------+
| DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR) |
+------------------------------------------------------------+
| 1899-12-30 14:00:00                                        |
+------------------------------------------------------------+
SELECT DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND);
+--------------------------------------------------------------------------------+
| DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND) |
+--------------------------------------------------------------------------------+
| 1993-01-01 00:00:01.000001                                                     |
+--------------------------------------------------------------------------------+

See Also

DATE_FORMAT

Syntax

DATE_FORMAT(date, format[, locale])

Description

Formats the date value according to the format string.

The language used for the names is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

The options that can be used by DATE_FORMAT(), as well as its inverse STR_TO_DATE() and the FROM_UNIXTIME() function, are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Monday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

To get a date in one of the standard formats, GET_FORMAT() can be used.

Examples

SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y');
+------------------------------------------------+
| DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y') |
+------------------------------------------------+
| Sunday October 2009                            |
+------------------------------------------------+

SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s');
+------------------------------------------------+
| DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s') |
+------------------------------------------------+
| 22:23:00                                       |
+------------------------------------------------+

SELECT DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j');
+------------------------------------------------------------+
| DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j') |
+------------------------------------------------------------+
| 4th 00 Thu 04 10 Oct 277                                   |
+------------------------------------------------------------+

SELECT DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w');
+------------------------------------------------------------+
| DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w') |
+------------------------------------------------------------+
| 22 22 10 10:23:00 PM 22:23:00 00 6                         |
+------------------------------------------------------------+

SELECT DATE_FORMAT('1999-01-01', '%X %V');
+------------------------------------+
| DATE_FORMAT('1999-01-01', '%X %V') |
+------------------------------------+
| 1998 52                            |
+------------------------------------+

SELECT DATE_FORMAT('2006-06-00', '%d');
+---------------------------------+
| DATE_FORMAT('2006-06-00', '%d') |
+---------------------------------+
| 00                              |
+---------------------------------+
MariaDB starting with 10.3.2

Optionally, the locale can be explicitly specified as the third DATE_FORMAT() argument. Doing so makes the function independent from the session settings, and the three argument version of DATE_FORMAT() can be used in virtual indexed and persistent generated-columns:

SELECT DATE_FORMAT('2006-01-01', '%W', 'el_GR');
+------------------------------------------+
| DATE_FORMAT('2006-01-01', '%W', 'el_GR') |
+------------------------------------------+
| Κυριακή                                  |
+------------------------------------------+

See Also

DATE_SUB

Syntax

DATE_SUB(date,INTERVAL expr unit)

Description

Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units.

See also DATE_ADD().

Examples

SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('1998-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 1997-12-02                              |
+-----------------------------------------+
SELECT DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND);
+----------------------------------------------------------------+
| DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND) |
+----------------------------------------------------------------+
| 2004-12-30 22:58:59                                            |
+----------------------------------------------------------------+

DAYNAME

Syntax

DAYNAME(date)

Description

Returns the name of the weekday for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

Examples

SELECT DAYNAME('2007-02-03');
+-----------------------+
| DAYNAME('2007-02-03') |
+-----------------------+
| Saturday              |
+-----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d, DAYNAME(d) FROM t1;
+---------------------+------------+
| d                   | DAYNAME(d) |
+---------------------+------------+
| 2007-01-30 21:31:07 | Tuesday    |
| 1983-10-15 06:42:51 | Saturday   |
| 2011-04-21 12:34:56 | Thursday   |
| 2011-10-30 06:31:41 | Sunday     |
| 2011-01-30 14:03:25 | Sunday     |
| 2004-10-07 11:19:34 | Thursday   |
+---------------------+------------+

Changing the locale:

SET lc_time_names = 'fr_CA';

SELECT DAYNAME('2013-04-01');
+-----------------------+
| DAYNAME('2013-04-01') |
+-----------------------+
| lundi                 |
+-----------------------+

DAYOFMONTH

Syntax

DAYOFMONTH(date)

Description

Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as '0000-00-00' or '2008-00-00' which have a zero day part.

DAY() is a synonym.

Examples

SELECT DAYOFMONTH('2007-02-03');
+--------------------------+
| DAYOFMONTH('2007-02-03') |
+--------------------------+
|                        3 |
+--------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d FROM t1 where DAYOFMONTH(d) = 30;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+

DAYOFWEEK

Syntax

DAYOFWEEK(date)

Description

Returns the day of the week index for the date (1 = Sunday, 2 = Monday, ..., 7 = Saturday). These index values correspond to the ODBC standard.

This contrasts with WEEKDAY() which follows a different index numbering (0 = Monday, 1 = Tuesday, ... 6 = Sunday).

Examples

SELECT DAYOFWEEK('2007-02-03');
+-------------------------+
| DAYOFWEEK('2007-02-03') |
+-------------------------+
|                       7 |
+-------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d, DAYNAME(d), DAYOFWEEK(d), WEEKDAY(d) from t1;
+---------------------+------------+--------------+------------+
| d                   | DAYNAME(d) | DAYOFWEEK(d) | WEEKDAY(d) |
+---------------------+------------+--------------+------------+
| 2007-01-30 21:31:07 | Tuesday    |            3 |          1 |
| 1983-10-15 06:42:51 | Saturday   |            7 |          5 |
| 2011-04-21 12:34:56 | Thursday   |            5 |          3 |
| 2011-10-30 06:31:41 | Sunday     |            1 |          6 |
| 2011-01-30 14:03:25 | Sunday     |            1 |          6 |
| 2004-10-07 11:19:34 | Thursday   |            5 |          3 |
+---------------------+------------+--------------+------------+

EXTRACT

Syntax

EXTRACT(unit FROM date)

Description

The EXTRACT() function extracts the required unit from the date. See Date and Time Units for a complete list of permitted units.

In MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM ...) was changed to return a value from 0 to 23, adhering to the SQL standard. Until MariaDB 10.0.6 and MariaDB 5.5.34, and in all versions of MySQL at least as of MySQL 5.7, it could return a value > 23. HOUR() is not a standard function, so continues to adhere to the old behaviour inherited from MySQL.

Examples

SELECT EXTRACT(YEAR FROM '2009-07-02');
+---------------------------------+
| EXTRACT(YEAR FROM '2009-07-02') |
+---------------------------------+
|                            2009 |
+---------------------------------+

SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
|                                         200907 |
+------------------------------------------------+

SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
|                                          20102 |
+------------------------------------------------+

SELECT EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123');
+--------------------------------------------------------+
| EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123') |
+--------------------------------------------------------+
|                                                    123 |
+--------------------------------------------------------+

From MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM...) returns a value from 0 to 23, as per the SQL standard. HOUR is not a standard function, so continues to adhere to the old behaviour inherited from MySQL.

SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
|                             2 |               26 |
+-------------------------------+------------------+

See Also

FROM_UNIXTIME

Syntax

FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format)

Description

Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. unix_timestamp is an internal timestamp value such as is produced by the UNIX_TIMESTAMP() function.

If format is given, the result is formatted according to the format string, which is used the same way as listed in the entry for the DATE_FORMAT() function.

Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a timestamp beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this.

The options that can be used by FROM_UNIXTIME(), as well as DATE_FORMAT() and STR_TO_DATE(), are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Sunday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

Performance Considerations

If your session time zone is set to SYSTEM (the default), FROM_UNIXTIME() will call the OS function to convert the data using the system time zone. At least on Linux, the corresponding function (localtime_r) uses a global mutex inside glibc that can cause contention under high concurrent load.

Set your time zone to a named time zone to avoid this issue. See mysql time zone tables for details on how to do this.

Examples

SELECT FROM_UNIXTIME(1196440219);
+---------------------------+
| FROM_UNIXTIME(1196440219) |
+---------------------------+
| 2007-11-30 11:30:19       |
+---------------------------+

SELECT FROM_UNIXTIME(1196440219) + 0;
+-------------------------------+
| FROM_UNIXTIME(1196440219) + 0 |
+-------------------------------+
|         20071130113019.000000 |
+-------------------------------+

SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x');
+---------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x') |
+---------------------------------------------------------+
| 2010 27th March 01:03:47 2010                           |
+---------------------------------------------------------+

See Also

GET_FORMAT

Syntax

GET_FORMAT({DATE|DATETIME|TIME}, {'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})

Description

Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions.

Possible result formats are:

Function CallResult Format
GET_FORMAT(DATE,'EUR')'%d.%m.%Y'
GET_FORMAT(DATE,'USA')'%m.%d.%Y'
GET_FORMAT(DATE,'JIS')'%Y-%m-%d'
GET_FORMAT(DATE,'ISO')'%Y-%m-%d'
GET_FORMAT(DATE,'INTERNAL')'%Y%m%d'
GET_FORMAT(DATETIME,'EUR')'%Y-%m-%d %H.%i.%s'
GET_FORMAT(DATETIME,'USA')'%Y-%m-%d %H.%i.%s'
GET_FORMAT(DATETIME,'JIS')'%Y-%m-%d %H:%i:%s'
GET_FORMAT(DATETIME,'ISO')'%Y-%m-%d %H:%i:%s'
GET_FORMAT(DATETIME,'INTERNAL')'%Y%m%d%H%i%s'
GET_FORMAT(TIME,'EUR')'%H.%i.%s'
GET_FORMAT(TIME,'USA')'%h:%i:%s %p'
GET_FORMAT(TIME,'JIS')'%H:%i:%s'
GET_FORMAT(TIME,'ISO')'%H:%i:%s'
GET_FORMAT(TIME,'INTERNAL')'%H%i%s'

Examples

Obtaining the string matching to the standard European date format:

SELECT GET_FORMAT(DATE, 'EUR');
+-------------------------+
| GET_FORMAT(DATE, 'EUR') |
+-------------------------+
| %d.%m.%Y                |
+-------------------------+

Using the same string to format a date:

SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR'));
+--------------------------------------------------+
| DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR')) |
+--------------------------------------------------+
| 03.10.2003                                       |
+--------------------------------------------------+

SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA'));
+--------------------------------------------------+
| STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA')) |
+--------------------------------------------------+
| 2003-10-31                                       |
+--------------------------------------------------+

HOUR

Syntax

HOUR(time)

Description

Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23.

The return value is always positive, even if a negative TIME value is provided.

Examples

SELECT HOUR('10:05:03');
+------------------+
| HOUR('10:05:03') |
+------------------+
|               10 |
+------------------+

SELECT HOUR('272:59:59');
+-------------------+
| HOUR('272:59:59') |
+-------------------+
|               272 |
+-------------------+

Difference between EXTRACT (HOUR FROM ...) (>= MariaDB 10.0.7 and MariaDB 5.5.35) and HOUR:

SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
|                             2 |               26 |
+-------------------------------+------------------+

See Also

LAST_DAY

Syntax

LAST_DAY(date)

Description

Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid.

Examples

SELECT LAST_DAY('2003-02-05');
+------------------------+
| LAST_DAY('2003-02-05') |
+------------------------+
| 2003-02-28             |
+------------------------+

SELECT LAST_DAY('2004-02-05');
+------------------------+
| LAST_DAY('2004-02-05') |
+------------------------+
| 2004-02-29             |
+------------------------+

SELECT LAST_DAY('2004-01-01 01:01:01');
+---------------------------------+
| LAST_DAY('2004-01-01 01:01:01') |
+---------------------------------+
| 2004-01-31                      |
+---------------------------------+

SELECT LAST_DAY('2003-03-32');
+------------------------+
| LAST_DAY('2003-03-32') |
+------------------------+
| NULL                   |
+------------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Incorrect datetime value: '2003-03-32'

MAKEDATE

Syntax

MAKEDATE(year,dayofyear)

Description

Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result is NULL.

Examples

SELECT MAKEDATE(2011,31), MAKEDATE(2011,32);
+-------------------+-------------------+
| MAKEDATE(2011,31) | MAKEDATE(2011,32) |
+-------------------+-------------------+
| 2011-01-31        | 2011-02-01        |
+-------------------+-------------------+

SELECT MAKEDATE(2011,365), MAKEDATE(2014,365);
+--------------------+--------------------+
| MAKEDATE(2011,365) | MAKEDATE(2014,365) |
+--------------------+--------------------+
| 2011-12-31         | 2014-12-31         |
+--------------------+--------------------+

SELECT MAKEDATE(2011,0);
+------------------+
| MAKEDATE(2011,0) |
+------------------+
| NULL             |
+------------------+

MAKETIME

Syntax

MAKETIME(hour,minute,second)

Description

Returns a time value calculated from the hour, minute, and second arguments.

If minute or second are out of the range 0 to 60, NULL is returned. The hour can be in the range -838 to 838, outside of which the value is truncated with a warning.

Examples

SELECT MAKETIME(13,57,33);
+--------------------+
| MAKETIME(13,57,33) |
+--------------------+
| 13:57:33           |
+--------------------+

SELECT MAKETIME(-13,57,33);
+---------------------+
| MAKETIME(-13,57,33) |
+---------------------+
| -13:57:33           |
+---------------------+

SELECT MAKETIME(13,67,33);
+--------------------+
| MAKETIME(13,67,33) |
+--------------------+
| NULL               |
+--------------------+

SELECT MAKETIME(-1000,57,33);
+-----------------------+
| MAKETIME(-1000,57,33) |
+-----------------------+
| -838:59:59            |
+-----------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-----------------------------------------------+
| Level   | Code | Message                                       |
+---------+------+-----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '-1000:57:33' |
+---------+------+-----------------------------------------------+

MICROSECOND

Syntax

MICROSECOND(expr)

Description

Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999.

If expr is a time with no microseconds, zero is returned, while if expr is a date with no time, zero with a warning is returned.

Examples

SELECT MICROSECOND('12:00:00.123456');
+--------------------------------+
| MICROSECOND('12:00:00.123456') |
+--------------------------------+
|                         123456 |
+--------------------------------+

SELECT MICROSECOND('2009-12-31 23:59:59.000010');
+-------------------------------------------+
| MICROSECOND('2009-12-31 23:59:59.000010') |
+-------------------------------------------+
|                                        10 |
+-------------------------------------------+

SELECT MICROSECOND('2013-08-07 12:13:14');
+------------------------------------+
| MICROSECOND('2013-08-07 12:13:14') |
+------------------------------------+
|                                  0 |
+------------------------------------+

SELECT MICROSECOND('2013-08-07');
+---------------------------+
| MICROSECOND('2013-08-07') |
+---------------------------+
|                         0 |
+---------------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------------+
| Level   | Code | Message                                      |
+---------+------+----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '2013-08-07' |
+---------+------+----------------------------------------------+

See Also

NOW

Syntax

NOW([precision])
CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])
LOCALTIME, LOCALTIME([precision])
LOCALTIMESTAMP
LOCALTIMESTAMP([precision])

Description

Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

NOW() (or its synonyms) can be used as the default value for TIMESTAMP columns as well as, since MariaDB 10.0.1, DATETIME columns. Before MariaDB 10.0.1, it was only possible for a single TIMESTAMP column per table to contain the CURRENT_TIMESTAMP as its default.

When displayed in the INFORMATION_SCHEMA.COLUMNS table, a default CURRENT TIMESTAMP is displayed as CURRENT_TIMESTAMP up until MariaDB 10.2.2, and as current_timestamp() from MariaDB 10.2.3, due to to MariaDB 10.2 accepting expressions in the DEFAULT clause.

Examples

SELECT NOW();
+---------------------+
| NOW()               |
+---------------------+
| 2010-03-27 13:13:25 |
+---------------------+

SELECT NOW() + 0;
+-----------------------+
| NOW() + 0             |
+-----------------------+
| 20100327131329.000000 |
+-----------------------+

With precision:

SELECT CURRENT_TIMESTAMP(2);
+------------------------+
| CURRENT_TIMESTAMP(2)   |
+------------------------+
| 2018-07-10 09:47:26.24 |
+------------------------+

Used as a default TIMESTAMP:

CREATE TABLE t (createdTS TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP);

From MariaDB 10.2.2:

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='test'
  AND COLUMN_NAME LIKE '%ts%'\G
*************************** 1. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t
             COLUMN_NAME: ts
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: current_timestamp()
...

<= MariaDB 10.2.1

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='test'
  AND COLUMN_NAME LIKE '%ts%'\G
*************************** 1. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t
             COLUMN_NAME: createdTS
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: CURRENT_TIMESTAMP
...

See Also

PERIOD_ADD

Syntax

PERIOD_ADD(P,N)

Description

Adds N months to period P. P is in the format YYMM or YYYYMM, and is not a date value. If P contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards.

Returns a value in the format YYYYMM.

Examples

SELECT PERIOD_ADD(200801,2);
+----------------------+
| PERIOD_ADD(200801,2) |
+----------------------+
|               200803 |
+----------------------+

SELECT PERIOD_ADD(6910,2);
+--------------------+
| PERIOD_ADD(6910,2) |
+--------------------+
|             206912 |
+--------------------+

SELECT PERIOD_ADD(7010,2);
+--------------------+
| PERIOD_ADD(7010,2) |
+--------------------+
|             197012 |
+--------------------+

PERIOD_DIFF

Syntax

PERIOD_DIFF(P1,P2)

Description

Returns the number of months between periods P1 and P2. P1 and P2 can be in the format YYMM or YYYYMM, and are not date values.

If P1 or P2 contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards.

Examples

SELECT PERIOD_DIFF(200802,200703);
+----------------------------+
| PERIOD_DIFF(200802,200703) |
+----------------------------+
|                         11 |
+----------------------------+

SELECT PERIOD_DIFF(6902,6803);
+------------------------+
| PERIOD_DIFF(6902,6803) |
+------------------------+
|                     11 |
+------------------------+

SELECT PERIOD_DIFF(7002,6803);
+------------------------+
| PERIOD_DIFF(7002,6803) |
+------------------------+
|                  -1177 |
+------------------------+

SEC_TO_TIME

Syntax

SEC_TO_TIME(seconds)

Description

Returns the seconds argument, converted to hours, minutes, and seconds, as a TIME value. The range of the result is constrained to that of the TIME data type. A warning occurs if the argument corresponds to a value outside that range.

The time will be returned in the format hh:mm:ss, or hhmmss if used in a numeric calculation.

Examples

SELECT SEC_TO_TIME(12414);
+--------------------+
| SEC_TO_TIME(12414) |
+--------------------+
| 03:26:54           |
+--------------------+

SELECT SEC_TO_TIME(12414)+0;
+----------------------+
| SEC_TO_TIME(12414)+0 |
+----------------------+
|                32654 |
+----------------------+

SELECT SEC_TO_TIME(9999999);
+----------------------+
| SEC_TO_TIME(9999999) |
+----------------------+
| 838:59:59            |
+----------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-------------------------------------------+
| Level   | Code | Message                                   |
+---------+------+-------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '9999999' |
+---------+------+-------------------------------------------+

STR_TO_DATE

Syntax

STR_TO_DATE(str,format)

Description

This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts.

The date, time, or datetime values contained in str should be given in the format indicated by format. If str contains an illegal date, time, or datetime value, STR_TO_DATE() returns NULL. An illegal value also produces a warning.

The options that can be used by STR_TO_DATE(), as well as its inverse DATE_FORMAT() and the FROM_UNIXTIME() function, are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Monday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

Examples

SELECT STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y');
+---------------------------------------------------------+
| STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y') |
+---------------------------------------------------------+
| 2014-06-02                                              |
+---------------------------------------------------------+


SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y');
+--------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y') |
+--------------------------------------------------------------+
| NULL                                                         |
+--------------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-----------------------------------------------------------------------------------+
| Level   | Code | Message                                                                           |
+---------+------+-----------------------------------------------------------------------------------+
| Warning | 1411 | Incorrect datetime value: 'Wednesday23423, June 2, 2014' for function str_to_date |
+---------+------+-----------------------------------------------------------------------------------+

SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y');
+----------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y') |
+----------------------------------------------------------------+
| 2014-06-02                                                     |
+----------------------------------------------------------------+

See Also

SUBDATE

Syntax

SUBDATE(date,INTERVAL expr unit), SUBDATE(expr,days)

Description

When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB(). See Date and Time Units for a complete list of permitted units.

The second form allows the use of an integer value for days. In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression expr.

Examples

SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2007-12-02                              |
+-----------------------------------------+

SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| SUBDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2007-12-02                             |
+----------------------------------------+
SELECT SUBDATE('2008-01-02 12:00:00', 31);
+------------------------------------+
| SUBDATE('2008-01-02 12:00:00', 31) |
+------------------------------------+
| 2007-12-02 12:00:00                |
+------------------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d, SUBDATE(d, 10) from t1;
+---------------------+---------------------+
| d                   | SUBDATE(d, 10)      |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-01-20 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-05 06:42:51 |
| 2011-04-21 12:34:56 | 2011-04-11 12:34:56 |
| 2011-10-30 06:31:41 | 2011-10-20 06:31:41 |
| 2011-01-30 14:03:25 | 2011-01-20 14:03:25 |
| 2004-10-07 11:19:34 | 2004-09-27 11:19:34 |
+---------------------+---------------------+

SELECT d, SUBDATE(d, INTERVAL 10 MINUTE) from t1;
+---------------------+--------------------------------+
| d                   | SUBDATE(d, INTERVAL 10 MINUTE) |
+---------------------+--------------------------------+
| 2007-01-30 21:31:07 | 2007-01-30 21:21:07            |
| 1983-10-15 06:42:51 | 1983-10-15 06:32:51            |
| 2011-04-21 12:34:56 | 2011-04-21 12:24:56            |
| 2011-10-30 06:31:41 | 2011-10-30 06:21:41            |
| 2011-01-30 14:03:25 | 2011-01-30 13:53:25            |
| 2004-10-07 11:19:34 | 2004-10-07 11:09:34            |
+---------------------+--------------------------------+

SUBTIME

Syntax

SUBTIME(expr1,expr2)

Description

SUBTIME() returns expr1 - expr2 expressed as a value in the same format as expr1. expr1 is a time or datetime expression, and expr2 is a time expression.

Examples

SELECT SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002');
+--------------------------------------------------------+
| SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002') |
+--------------------------------------------------------+
| 2007-12-30 22:58:58.999997                             |
+--------------------------------------------------------+

SELECT SUBTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| SUBTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| -00:59:59.999999                              |
+-----------------------------------------------+

SYSDATE

Syntax

SYSDATE([precision])

Description

Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

SYSDATE() returns the time at which it executes. This differs from the behavior for NOW(), which returns a constant time that indicates the time at which the statement began to execute. (Within a stored routine or trigger, NOW() returns the time at which the routine or triggering statement began to execute.)

In addition, changing the timestamp system variable with a SET timestamp statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE().

Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is non-deterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging, or start the server with the mysqld option --sysdate-is-now to cause SYSDATE() to be an alias for NOW(). The non-deterministic nature of SYSDATE() also means that indexes cannot be used for evaluating expressions that refer to it, and that statements using the SYSDATE() function are unsafe for statement-based replication.

Examples

Difference between NOW() and SYSDATE():

SELECT NOW(), SLEEP(2), NOW();
+---------------------+----------+---------------------+
| NOW()               | SLEEP(2) | NOW()               |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:40 |        0 | 2010-03-27 13:23:40 |
+---------------------+----------+---------------------+

SELECT SYSDATE(), SLEEP(2), SYSDATE();
+---------------------+----------+---------------------+
| SYSDATE()           | SLEEP(2) | SYSDATE()           |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:52 |        0 | 2010-03-27 13:23:54 |
+---------------------+----------+---------------------+

With precision:

SELECT SYSDATE(4);
+--------------------------+
| SYSDATE(4)               |
+--------------------------+
| 2018-07-10 10:17:13.1689 |
+--------------------------+

See Also

TIMEDIFF

Syntax

TIMEDIFF(expr1,expr2)

Description

TIMEDIFF() returns expr1 - expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type.

Examples

SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001');
+---------------------------------------------------------------+
| TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001') |
+---------------------------------------------------------------+
| -00:00:00.000001                                              |
+---------------------------------------------------------------+

SELECT TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002');
+----------------------------------------------------------------------+
| TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002') |
+----------------------------------------------------------------------+
| 46:58:57.999999                                                      |
+----------------------------------------------------------------------+

TIMESTAMP FUNCTION

Syntax

TIMESTAMP(expr), TIMESTAMP(expr1,expr2)

Description

With a single argument, this function returns the date or datetime expression expr as a datetime value. With two arguments, it adds the time expression expr2 to the date or datetime expression expr1 and returns the result as a datetime value.

Examples

SELECT TIMESTAMP('2003-12-31');
+-------------------------+
| TIMESTAMP('2003-12-31') |
+-------------------------+
| 2003-12-31 00:00:00     |
+-------------------------+

SELECT TIMESTAMP('2003-12-31 12:00:00','6:30:00');
+--------------------------------------------+
| TIMESTAMP('2003-12-31 12:00:00','6:30:00') |
+--------------------------------------------+
| 2003-12-31 18:30:00                        |
+--------------------------------------------+

TIMESTAMPADD

Syntax

TIMESTAMPADD(unit,interval,datetime_expr)

Description

Adds the integer expression interval to the date or datetime expression datetime_expr. The unit for interval is given by the unit argument, which should be one of the following values: MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

The unit value may be specified using one of keywords as shown, or with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are legal.

Before MariaDB 5.5, FRAC_SECOND was permitted as a synonym for MICROSECOND.

Examples

SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02');
+-------------------------------------+
| TIMESTAMPADD(MINUTE,1,'2003-01-02') |
+-------------------------------------+
| 2003-01-02 00:01:00                 |
+-------------------------------------+

SELECT TIMESTAMPADD(WEEK,1,'2003-01-02');
+-----------------------------------+
| TIMESTAMPADD(WEEK,1,'2003-01-02') |
+-----------------------------------+
| 2003-01-09                        |
+-----------------------------------+

TIMESTAMPDIFF

Syntax

TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2)

Description

Returns datetime_expr2 - datetime_expr1, where datetime_expr1 and datetime_expr2 are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part '00:00:00' where necessary. The unit for the result (an integer) is given by the unit argument. The legal values for unit are the same as those listed in the description of the TIMESTAMPADD() function, i.e MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

TIMESTAMPDIFF can also be used to calculate age.

Examples

SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01');
+------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01') |
+------------------------------------------------+
|                                              3 |
+------------------------------------------------+

SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01');
+-----------------------------------------------+
| TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01') |
+-----------------------------------------------+
|                                            -1 |
+-----------------------------------------------+

SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55');
+----------------------------------------------------------+
| TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55') |
+----------------------------------------------------------+
|                                                   128885 |
+----------------------------------------------------------+

Calculating age:

SELECT CURDATE();
+------------+
| CURDATE()  |
+------------+
| 2019-05-27 |
+------------+

SELECT TIMESTAMPDIFF(YEAR, '1971-06-06', CURDATE()) AS age;
+------+
| age  |
+------+
|   47 |
+------+

SELECT TIMESTAMPDIFF(YEAR, '1971-05-06', CURDATE()) AS age;
+------+
| age  |
+------+
|   48 |
+------+

Age as of 2014-08-02:

SELECT name, date_of_birth, TIMESTAMPDIFF(YEAR,date_of_birth,'2014-08-02') AS age 
  FROM student_details;
+---------+---------------+------+
| name    | date_of_birth | age  |
+---------+---------------+------+
| Chun    | 1993-12-31    |   20 |
| Esben   | 1946-01-01    |   68 |
| Kaolin  | 1996-07-16    |   18 |
| Tatiana | 1988-04-13    |   26 |
+---------+---------------+------+

TO_DAYS

Syntax

TO_DAYS(date)

Description

Given a date date, returns the number of days since the start of the current calendar (0000-00-00).

The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar.

This is the converse of the FROM_DAYS() function.

Examples

SELECT TO_DAYS('2007-10-07');
+-----------------------+
| TO_DAYS('2007-10-07') |
+-----------------------+
|                733321 |
+-----------------------+

SELECT TO_DAYS('0000-01-01');
+-----------------------+
| TO_DAYS('0000-01-01') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT TO_DAYS(950501);
+-----------------+
| TO_DAYS(950501) |
+-----------------+
|          728779 |
+-----------------+

TO_SECONDS

Syntax

TO_SECONDS(expr)

Description

Returns the number of seconds from year 0 till expr, or NULL if expr is not a valid date or datetime.

Examples

SELECT TO_SECONDS('2013-06-13');
+--------------------------+
| TO_SECONDS('2013-06-13') |
+--------------------------+
|              63538300800 |
+--------------------------+

SELECT TO_SECONDS('2013-06-13 21:45:13');
+-----------------------------------+
| TO_SECONDS('2013-06-13 21:45:13') |
+-----------------------------------+
|                       63538379113 |
+-----------------------------------+

SELECT TO_SECONDS(NOW());
+-------------------+
| TO_SECONDS(NOW()) |
+-------------------+
|       63543530875 |
+-------------------+

SELECT TO_SECONDS(20130513);
+----------------------+
| TO_SECONDS(20130513) |
+----------------------+
|          63535622400 |
+----------------------+
1 row in set (0.00 sec)

SELECT TO_SECONDS(130513);
+--------------------+
| TO_SECONDS(130513) |
+--------------------+
|        63535622400 |
+--------------------+

UNIX_TIMESTAMP

Syntax

UNIX_TIMESTAMP()
UNIX_TIMESTAMP(date)

Description

If called with no argument, returns a Unix timestamp (seconds since '1970-01-01 00:00:00' UTC) as an unsigned integer. If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' UTC. date may be a DATE string, a DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or YYYYMMDD. The server interprets date as a value in the current time zone and converts it to an internal value in UTC. Clients can set their time zone as described in time zones.

The inverse function of UNIX_TIMESTAMP() is FROM_UNIXTIME()

UNIX_TIMESTAMP() supports microseconds.

Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a date beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this.

Error Handling

Returns NULL for wrong arguments to UNIX_TIMESTAMP(). In MySQL and MariaDB before 5.3 wrong arguments to UNIX_TIMESTAMP() returned 0.

Compatibility

As you can see in the examples above, UNIX_TIMESTAMP(constant-date-string) returns a timestamp with 6 decimals while MariaDB 5.2 and before returns it without decimals. This can cause a problem if you are using UNIX_TIMESTAMP() as a partitioning function. You can fix this by using FLOOR(UNIX_TIMESTAMP(..)) or changing the date string to a date number, like 20080101000000.

Examples

SELECT UNIX_TIMESTAMP();
+------------------+
| UNIX_TIMESTAMP() |
+------------------+
|       1269711082 |
+------------------+

SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19');
+---------------------------------------+
| UNIX_TIMESTAMP('2007-11-30 10:30:19') |
+---------------------------------------+
|                     1196436619.000000 |
+---------------------------------------+

SELECT UNIX_TIMESTAMP("2007-11-30 10:30:19.123456");
+----------------------------------------------+
| unix_timestamp("2007-11-30 10:30:19.123456") |
+----------------------------------------------+
|                            1196411419.123456 |
+----------------------------------------------+

SELECT FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19'));
+------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19')) |
+------------------------------------------------------+
| 2007-11-30 10:30:19.000000                           |
+------------------------------------------------------+

SELECT FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19')));
+-------------------------------------------------------------+
| FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19'))) |
+-------------------------------------------------------------+
| 2007-11-30 10:30:19                                         |
+-------------------------------------------------------------+

See Also

UTC_TIMESTAMP

Syntax

UTC_TIMESTAMP
UTC_TIMESTAMP([precision])

Description

Returns the current UTC date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
+---------------------+-----------------------+
| UTC_TIMESTAMP()     | UTC_TIMESTAMP() + 0   |
+---------------------+-----------------------+
| 2010-03-27 17:33:16 | 20100327173316.000000 |
+---------------------+-----------------------+

With precision:

SELECT UTC_TIMESTAMP(4);
+--------------------------+
| UTC_TIMESTAMP(4)         |
+--------------------------+
| 2018-07-10 07:51:09.1019 |
+--------------------------+

See Also

WEEK

Syntax

WEEK(date[,mode])

Description

This function returns the week number for date. The two-argument form of WEEK() allows you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the value of the default_week_format system variable is used.

Modes

Mode1st day of weekRangeWeek 1 is the 1st week with
0Sunday0-53a Sunday in this year
1Monday0-53more than 3 days this year
2Sunday1-53a Sunday in this year
3Monday1-53more than 3 days this year
4Sunday0-53more than 3 days this year
5Monday0-53a Monday in this year
6Sunday1-53more than 3 days this year
7Monday1-53a Monday in this year

With the mode value of 3, which means “more than 3 days this year”, weeks are numbered according to ISO 8601:1988.

Examples

SELECT WEEK('2008-02-20');
+--------------------+
| WEEK('2008-02-20') |
+--------------------+
|                  7 |
+--------------------+

SELECT WEEK('2008-02-20',0);
+----------------------+
| WEEK('2008-02-20',0) |
+----------------------+
|                    7 |
+----------------------+

SELECT WEEK('2008-02-20',1);
+----------------------+
| WEEK('2008-02-20',1) |
+----------------------+
|                    8 |
+----------------------+

SELECT WEEK('2008-12-31',0);
+----------------------+
| WEEK('2008-12-31',0) |
+----------------------+
|                   52 |
+----------------------+

SELECT WEEK('2008-12-31',1);
+----------------------+
| WEEK('2008-12-31',1) |
+----------------------+
|                   53 |
+----------------------+

 SELECT WEEK('2019-12-30',3);
+----------------------+
| WEEK('2019-12-30',3) |
+----------------------+
|                    1 |
+----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d, WEEK(d,0), WEEK(d,1) from t1;
+---------------------+-----------+-----------+
| d                   | WEEK(d,0) | WEEK(d,1) |
+---------------------+-----------+-----------+
| 2007-01-30 21:31:07 |         4 |         5 |
| 1983-10-15 06:42:51 |        41 |        41 |
| 2011-04-21 12:34:56 |        16 |        16 |
| 2011-10-30 06:31:41 |        44 |        43 |
| 2011-01-30 14:03:25 |         5 |         4 |
| 2004-10-07 11:19:34 |        40 |        41 |
+---------------------+-----------+-----------+

WEEKDAY

Syntax

WEEKDAY(date)

Description

Returns the weekday index for date (0 = Monday, 1 = Tuesday, ... 6 = Sunday).

This contrasts with DAYOFWEEK() which follows the ODBC standard (1 = Sunday, 2 = Monday, ..., 7 = Saturday).

Examples

SELECT WEEKDAY('2008-02-03 22:23:00');
+--------------------------------+
| WEEKDAY('2008-02-03 22:23:00') |
+--------------------------------+
|                              6 |
+--------------------------------+

SELECT WEEKDAY('2007-11-06');
+-----------------------+
| WEEKDAY('2007-11-06') |
+-----------------------+
|                     1 |
+-----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT d FROM t1 where WEEKDAY(d) = 6;
+---------------------+
| d                   |
+---------------------+
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+

WEEKOFYEAR

Syntax

WEEKOFYEAR(date)

Description

Returns the calendar week of the date as a number in the range from 1 to 53. WEEKOFYEAR() is a compatibility function that is equivalent to WEEK(date,3).

Examples

SELECT WEEKOFYEAR('2008-02-20');
+--------------------------+
| WEEKOFYEAR('2008-02-20') |
+--------------------------+
|                        8 |
+--------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
 select * from t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
SELECT d, WEEKOFYEAR(d), WEEK(d,3) from t1;
+---------------------+---------------+-----------+
| d                   | WEEKOFYEAR(d) | WEEK(d,3) |
+---------------------+---------------+-----------+
| 2007-01-30 21:31:07 |             5 |         5 |
| 1983-10-15 06:42:51 |            41 |        41 |
| 2011-04-21 12:34:56 |            16 |        16 |
| 2011-10-30 06:31:41 |            43 |        43 |
| 2011-01-30 14:03:25 |             4 |         4 |
| 2004-10-07 11:19:34 |            41 |        41 |
+---------------------+---------------+-----------+

YEAR

Syntax

YEAR(date)

Description

Returns the year for the given date, in the range 1000 to 9999, or 0 for the "zero" date.

Examples

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+

SELECT * FROM t1 WHERE YEAR(d) = 2011;
+---------------------+
| d                   |
+---------------------+
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+
SELECT YEAR('1987-01-01');
+--------------------+
| YEAR('1987-01-01') |
+--------------------+
|               1987 |
+--------------------+

See Also

YEARWEEK

Syntax

YEARWEEK(date), YEARWEEK(date,mode)

Description

Returns year and week for a date. The mode argument works exactly like the mode argument to WEEK(). The year in the result may be different from the year in the date argument for the first and the last week of the year.

Examples

SELECT YEARWEEK('1987-01-01');
+------------------------+
| YEARWEEK('1987-01-01') |
+------------------------+
|                 198652 |
+------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
6 rows in set (0.02 sec)
SELECT YEARWEEK(d) FROM t1 WHERE YEAR(d) = 2011;
+-------------+
| YEARWEEK(d) |
+-------------+
|      201116 |
|      201144 |
|      201105 |
+-------------+
3 rows in set (0.03 sec)

Well-Known Binary (WKB) Format

WKB stands for Well-Known Binary, a format for representing geographical and geometrical data.

WKB uses 1-byte unsigned integers, 4-byte unsigned integers, and 8-byte double-precision numbers.

  • The first byte indicates the byte order. 00 for big endian, or 01 for little endian.
  • The next 4 bytes indicate the geometry type. Values from 1 to 7 indicate whether the type is Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection respectively.
  • The 8-byte floats represent the co-ordinates.

Take the following example, a sequence of 21 bytes each represented by two hex digits:

000000000140000000000000004010000000000000
  • It's big endian
    • 000000000140000000000000004010000000000000
  • It's a POINT
    • 000000000140000000000000004010000000000000
  • The X co-ordinate is 2.0
    • 000000000140000000000000004010000000000000
  • The Y-co-ordinate is 4.0
    • 000000000140000000000000004010000000000000

MPolyFromWKB

Syntax

MPolyFromWKB(wkb[,srid])
MultiPolygonFromWKB(wkb[,srid])

Description

Constructs a MULTIPOLYGON value using its WKB representation and SRID.

MPolyFromWKB() and MultiPolygonFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(MPointFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))'));

SELECT ST_AsText(MPolyFromWKB(@g));
+---------------------------------------------------------------------------------------------------------------+
| ST_AsText(MPolyFromWKB(@g))                                                                                   |
+---------------------------------------------------------------------------------------------------------------+
| MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18))) |
+---------------------------------------------------------------------------------------------------------------+

ST_GeomCollFromWKB

Syntax

ST_GeomCollFromWKB(wkb[,srid])
ST_GeometryCollectionFromWKB(wkb[,srid])
GeomCollFromWKB(wkb[,srid])
GeometryCollectionFromWKB(wkb[,srid])

Description

Constructs a GEOMETRYCOLLECTION value using its WKB representation and SRID.

ST_GeomCollFromWKB(), ST_GeometryCollectionFromWKB(), GeomCollFromWKB() and GeometryCollectionFromWKB() are synonyms.

Examples

SET @g = ST_AsBinary(ST_GeomFromText('GEOMETRYCOLLECTION(POLYGON((5 5,10 5,10 10,5 5)),POINT(10 10))'));

SELECT ST_AsText(ST_GeomCollFromWKB(@g));
+----------------------------------------------------------------+
| ST_AsText(ST_GeomCollFromWKB(@g))                              |
+----------------------------------------------------------------+
| GEOMETRYCOLLECTION(POLYGON((5 5,10 5,10 10,5 5)),POINT(10 10)) |
+----------------------------------------------------------------+

ST_BOUNDARY

MariaDB starting with 10.1.2

The ST_BOUNDARY function was introduced in MariaDB 10.1.2

Syntax

ST_BOUNDARY(g)
BOUNDARY(g)

Description

Returns a geometry that is the closure of the combinatorial boundary of the geometry value g.

BOUNDARY() is a synonym.

Examples

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)')));
+----------------------------------------------------------------------+
| ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)'))) |
+----------------------------------------------------------------------+
| MULTIPOINT(3 3,-3 3)                                                 |
+----------------------------------------------------------------------+

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))')));
+--------------------------------------------------------------------------+
| ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))'))) |
+--------------------------------------------------------------------------+
| LINESTRING(3 3,0 0,-3 3,3 3)                                             |
+--------------------------------------------------------------------------+

ST_ENVELOPE

Syntax

ST_ENVELOPE(g)
ENVELOPE(g)

Description

Returns the Minimum Bounding Rectangle (MBR) for the geometry value g. The result is returned as a Polygon value.

The polygon is defined by the corner points of the bounding box:

POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))

ST_ENVELOPE() and ENVELOPE() are synonyms.

Examples

SELECT AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4 4)')));
+----------------------------------------------------------+
| AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4 4)'))) |
+----------------------------------------------------------+
| POLYGON((1 1,4 1,4 4,1 4,1 1))                           |
+----------------------------------------------------------+

ST_ISCLOSED

Syntax

ST_IsClosed(g)
IsClosed(g)

Description

Returns 1 if a given LINESTRING's start and end points are the same, or 0 if they are not the same. Before MariaDB 10.1.5, returns NULL if not given a LINESTRING. After MariaDB 10.1.5, returns -1.

ST_IsClosed() and IsClosed() are synonyms.

Examples

SET @ls = 'LineString(0 0, 0 4, 4 4, 0 0)';
SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls));
+--------------------------------+
| ST_ISCLOSED(GEOMFROMTEXT(@ls)) |
+--------------------------------+
|                              1 |
+--------------------------------+

SET @ls = 'LineString(0 0, 0 4, 4 4, 0 1)';
SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls));
+--------------------------------+
| ST_ISCLOSED(GEOMFROMTEXT(@ls)) |
+--------------------------------+
|                              0 |
+--------------------------------+

BINARY Operator

This page describes the BINARY operator. For details about the data type, see Binary Data Type.

Syntax

BINARY

Description

The BINARY operator casts the string following it to a binary string. This is an easy way to force a column comparison to be done byte by byte rather than character by character. This causes the comparison to be case sensitive even if the column isn't defined as BINARY or BLOB.

BINARY also causes trailing spaces to be significant.

Examples

SELECT 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
|         1 |
+-----------+

SELECT BINARY 'a' = 'A';
+------------------+
| BINARY 'a' = 'A' |
+------------------+
|                0 |
+------------------+

SELECT 'a' = 'a ';
+------------+
| 'a' = 'a ' |
+------------+
|          1 |
+------------+

SELECT BINARY 'a' = 'a ';
+-------------------+
| BINARY 'a' = 'a ' |
+-------------------+
|                 0 |
+-------------------+

CAST

Syntax

CAST(expr AS type)

Description

The CAST() function takes a value of one type and produces a value of another type, similar to the CONVERT() function.

The type can be one of the following values:

The main difference between CAST and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax.

In MariaDB 10.4 and later, you can use the CAST() function with the INTERVAL keyword.

MariaDB starting with 5.5.31

Until MariaDB 5.5.31, X'HHHH', the standard SQL syntax for binary string literals, erroneously worked in the same way as 0xHHHH. In 5.5.31 it was intentionally changed to behave as a string in all contexts (and never as a number).

This introduces an incompatibility with previous versions of MariaDB, and all versions of MySQL (see the example below).

Examples

Simple casts:

SELECT CAST("abc" AS BINARY);
SELECT CAST("1" AS UNSIGNED INTEGER);
SELECT CAST(123 AS CHAR CHARACTER SET utf8)

Note that when one casts to CHAR without specifying the character set, the collation_connection character set collation will be used. When used with CHAR CHARACTER SET, the default collation for that character set will be used.

SELECT COLLATION(CAST(123 AS CHAR));
+------------------------------+
| COLLATION(CAST(123 AS CHAR)) |
+------------------------------+
| latin1_swedish_ci            |
+------------------------------+

SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8));
+-------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)) |
+-------------------------------------------------+
| utf8_general_ci                                 |
+-------------------------------------------------+

If you also want to change the collation, you have to use the COLLATE operator:

SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) 
  COLLATE utf8_unicode_ci);
+-------------------------------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) COLLATE utf8_unicode_ci) |
+-------------------------------------------------------------------------+
| utf8_unicode_ci                                                         |
+-------------------------------------------------------------------------+

Using CAST() to order an ENUM field as a CHAR rather than the internal numerical value:

CREATE TABLE enum_list (enum_field enum('c','a','b'));

INSERT INTO enum_list (enum_field) 
VALUES('c'),('a'),('c'),('b');

SELECT * FROM enum_list 
ORDER BY enum_field;
+------------+
| enum_field |
+------------+
| c          |
| c          |
| a          |
| b          |
+------------+

SELECT * FROM enum_list 
ORDER BY CAST(enum_field AS CHAR);
+------------+
| enum_field |
+------------+
| a          |
| b          |
| c          |
| c          |
+------------+

From MariaDB 5.5.31, the following will trigger warnings, since x'aa' and 'X'aa' no longer behave as a number. Previously, and in all versions of MySQL, no warnings are triggered since they did erroneously behave as a number:

SELECT CAST(0xAA AS UNSIGNED), CAST(x'aa' AS UNSIGNED), CAST(X'aa' AS UNSIGNED);
+------------------------+-------------------------+-------------------------+
| CAST(0xAA AS UNSIGNED) | CAST(x'aa' AS UNSIGNED) | CAST(X'aa' AS UNSIGNED) |
+------------------------+-------------------------+-------------------------+
|                    170 |                       0 |                       0 |
+------------------------+-------------------------+-------------------------+
1 row in set, 2 warnings (0.00 sec)

Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA'
Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA'

Casting to intervals:

SELECT CAST(2019-01-04 INTERVAL AS DAY_SECOND(2)) AS "Cast";

+-------------+
| Cast        |
+-------------+
| 00:20:17.00 |
+-------------+

See Also

CHAR Function

Syntax

CHAR(N,... [USING charset_name])

Description

CHAR() interprets each argument as an INT and returns a string consisting of the characters given by the code values of those integers. NULL values are skipped. By default, CHAR() returns a binary string. To produce a string in a given character set, use the optional USING clause:

SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8));
+---------------------+--------------------------------+
| CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) |
+---------------------+--------------------------------+
| binary              | utf8                           |
+---------------------+--------------------------------+

If USING is given and the result string is illegal for the given character set, a warning is issued. Also, if strict SQL mode is enabled, the result from CHAR() becomes NULL.

Examples

SELECT CHAR(77,97,114,'105',97,'68',66);
+----------------------------------+
| CHAR(77,97,114,'105',97,'68',66) |
+----------------------------------+
| MariaDB                          |
+----------------------------------+

SELECT CHAR(77,77.3,'77.3');
+----------------------+
| CHAR(77,77.3,'77.3') |
+----------------------+
| MMM                  |
+----------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect INTEGER value: '77.3'

See Also

CHAR_LENGTH

Syntax

CHAR_LENGTH(str)
CHARACTER_LENGTH(str)

Description

Returns the length of the given string argument, measured in characters. A multi-byte character counts as a single character. This means that for a string containing five two-byte characters, LENGTH() (or OCTET_LENGTH() in Oracle mode) returns 10, whereas CHAR_LENGTH() returns 5. If the argument is NULL, it returns NULL.

If the argument is not a string value, it is converted into a string.

It is synonymous with the CHARACTER_LENGTH() function.

Examples

SELECT CHAR_LENGTH('MariaDB');
+------------------------+
| CHAR_LENGTH('MariaDB') |
+------------------------+
|                      7 |
+------------------------+

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

CHR

MariaDB starting with 10.3.1

The CHR() function was introduced in MariaDB 10.3.1 to provide Oracle compatibility

Syntax

CHR(N)

Description

CHR() interprets each argument N as an integer and returns a VARCHAR(1) string consisting of the character given by the code values of the integer. The character set and collation of the string are set according to the values of the character_set_database and collation_database system variables.

CHR() is similar to the CHAR() function, but only accepts a single argument.

CHR() is available in all sql_modes.

Examples

SELECT CHR(67);
+---------+
| CHR(67) |
+---------+
| C       |
+---------+

SELECT CHR('67');
+-----------+
| CHR('67') |
+-----------+
| C         |
+-----------+

SELECT CHR('C');
+----------+
| CHR('C') |
+----------+
|          |
+----------+
1 row in set, 1 warning (0.000 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1292 | Truncated incorrect INTEGER value: 'C' |
+---------+------+----------------------------------------+

See Also

CONCAT

Syntax

CONCAT(str1,str2,...)

Description

Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are non-binary strings, the result is a non-binary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent binary string form; if you want to avoid that, you can use an explicit type cast, as in this example:

SELECT CONCAT(CAST(int_col AS CHAR), char_col);

CONCAT() returns NULL if any argument is NULL.

A NULL parameter hides all information contained in other parameters from the result. Sometimes this is not desirable; to avoid this, you can:

  • Use the CONCAT_WS() function with an empty separator, because that function is NULL-safe.
  • Use IFNULL() to turn NULLs into empty strings.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, CONCAT ignores NULL.

Examples

SELECT CONCAT('Ma', 'ria', 'DB');
+---------------------------+
| CONCAT('Ma', 'ria', 'DB') |
+---------------------------+
| MariaDB                   |
+---------------------------+

SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| NULL                            |
+---------------------------------+

SELECT CONCAT(42.0);
+--------------+
| CONCAT(42.0) |
+--------------+
| 42.0         |
+--------------+

Using IFNULL() to handle NULLs:

SELECT CONCAT('The value of @v is: ', IFNULL(@v, ''));
+------------------------------------------------+
| CONCAT('The value of @v is: ', IFNULL(@v, '')) |
+------------------------------------------------+
| The value of @v is:                            |
+------------------------------------------------+

In Oracle mode, from MariaDB 10.3:

SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| MariaDB                         |
+---------------------------------+

See Also

CONCAT_WS

Syntax

CONCAT_WS(separator,str1,str2,...)

Description

CONCAT_WS() stands for Concatenate With Separator and is a special form of CONCAT(). The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments.

If the separator is NULL, the result is NULL; all other NULL values are skipped. This makes CONCAT_WS() suitable when you want to concatenate some values and avoid losing all information if one of them is NULL.

Examples

SELECT CONCAT_WS(',','First name','Second name','Last Name');
+-------------------------------------------------------+
| CONCAT_WS(',','First name','Second name','Last Name') |
+-------------------------------------------------------+
| First name,Second name,Last Name                      |
+-------------------------------------------------------+

SELECT CONCAT_WS('-','Floor',NULL,'Room');
+------------------------------------+
| CONCAT_WS('-','Floor',NULL,'Room') |
+------------------------------------+
| Floor-Room                         |
+------------------------------------+

In some cases, remember to include a space in the separator string:

SET @a = 'gnu', @b = 'penguin', @c = 'sea lion';
Query OK, 0 rows affected (0.00 sec)

SELECT CONCAT_WS(', ', @a, @b, @c);
+-----------------------------+
| CONCAT_WS(', ', @a, @b, @c) |
+-----------------------------+
| gnu, penguin, sea lion      |
+-----------------------------+

Using CONCAT_WS() to handle NULLs:

SET @a = 'a', @b = NULL, @c = 'c';

SELECT CONCAT_WS('', @a, @b, @c);
+---------------------------+
| CONCAT_WS('', @a, @b, @c) |
+---------------------------+
| ac                        |
+---------------------------+

See Also

CONVERT

Syntax

CONVERT(expr,type), CONVERT(expr USING transcoding_name)

Description

The CONVERT() and CAST() functions take a value of one type and produce a value of another type.

The type can be one of the following values:

Note that in MariaDB, INT and INTEGER are the same thing.

BINARY produces a string with the BINARY data type. If the optional length is given, BINARY(N) causes the cast to use no more than N bytes of the argument. Values shorter than the given number in bytes are padded with 0x00 bytes to make them equal the length value.

CHAR(N) causes the cast to use no more than the number of characters given in the argument.

The main difference between the CAST() and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax.

CONVERT() with USING is used to convert data between different character sets. In MariaDB, transcoding names are the same as the corresponding character set names. For example, this statement converts the string 'abc' in the default character set to the corresponding string in the utf8 character set:

SELECT CONVERT('abc' USING utf8);

Examples

SELECT enum_col FROM tbl_name 
ORDER BY CAST(enum_col AS CHAR);

Converting a BINARY to string to permit the LOWER function to work:

SET @x = 'AardVark';

SET @x = BINARY 'AardVark';

SELECT LOWER(@x), LOWER(CONVERT (@x USING latin1));
+-----------+----------------------------------+
| LOWER(@x) | LOWER(CONVERT (@x USING latin1)) |
+-----------+----------------------------------+
| AardVark  | aardvark                         |
+-----------+----------------------------------+

See Also

ELT

Syntax

ELT(N, str1[, str2, str3,...])

Description

Takes a numeric argument and a series of string arguments. Returns the string that corresponds to the given numeric position. For instance, it returns str1 if N is 1, str2 if N is 2, and so on. If the numeric argument is a FLOAT, MariaDB rounds it to the nearest INTEGER. If the numeric argument is less than 1, greater than the total number of arguments, or not a number, ELT() returns NULL. It must have at least two arguments.

It is complementary to the FIELD() function.

Examples

SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(1, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| ej                                 |
+------------------------------------+

SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(4, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| foo                                |
+------------------------------------+

See also

  • FIND_IN_SET() function. Returns the position of a string in a set of strings.
  • FIELD() function. Returns the index position of a string in a list.

EXPORT_SET

Syntax

EXPORT_SET(bits, on, off[, separator[, number_of_bits]])

Description

Takes a minimum of three arguments. Returns a string where each bit in the given bits argument is returned, with the string values given for on and off.

Bits are examined from right to left, (from low-order to high-order bits). Strings are added to the result from left to right, separated by a separator string (defaults as ','). You can optionally limit the number of bits the EXPORT_SET() function examines using the number_of_bits option.

If any of the arguments are set as NULL, the function returns NULL.

Examples

SELECT EXPORT_SET(5,'Y','N',',',4);
+-----------------------------+
| EXPORT_SET(5,'Y','N',',',4) |
+-----------------------------+
| Y,N,Y,N                     |
+-----------------------------+

SELECT EXPORT_SET(6,'1','0',',',10);
+------------------------------+
| EXPORT_SET(6,'1','0',',',10) |
+------------------------------+
| 0,1,1,0,0,0,0,0,0,0          |
+------------------------------+

FIELD

Syntax

FIELD(pattern, str1[,str2,...])

Description

Returns the index position of the string or number matching the given pattern. Returns 0 in the event that none of the arguments match the pattern. Raises an Error 1582 if not given at least two arguments.

When all arguments given to the FIELD() function are strings, they are treated as case-insensitive. When all the arguments are numbers, they are treated as numbers. Otherwise, they are treated as doubles.

If the given pattern occurs more than once, the FIELD() function only returns the index of the first instance. If the given pattern is NULL, the function returns 0, as a NULL pattern always fails to match.

This function is complementary to the ELT() function.

Examples

SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo') 
   AS 'Field Results';
+---------------+
| Field Results | 
+---------------+
|             2 |
+---------------+

SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej', 'foo')
   AS 'Field Results';
+---------------+
| Field Results | 
+---------------+
|             0 |
+---------------+

SELECT FIELD(1, 2, 3, 4, 5, 1) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
|             5 |
+---------------+

SELECT FIELD(NULL, 2, 3) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
|             0 |
+---------------+

SELECT FIELD('fail') AS 'Field Results';
Error 1582 (42000): Incorrect parameter count in call
to native function 'field'

See also

  • ELT() function. Returns the N'th element from a set of strings.

EXTRACTVALUE

Syntax

EXTRACTVALUE(xml_frag, xpath_expr)

Description

The EXTRACTVALUE() function takes two string arguments: a fragment of XML markup and an XPath expression, (also known as a locator). It returns the text (That is, CDDATA), of the first text node which is a child of the element or elements matching the XPath expression.

In cases where a valid XPath expression does not match any text nodes in a valid XML fragment, (including the implicit /text() expression), the EXTRACTVALUE() function returns an empty string.

Invalid Arguments

When either the XML fragment or the XPath expression is NULL, the EXTRACTVALUE() function returns NULL. When the XML fragment is invalid, it raises a warning Code 1525:

Warning (Code 1525): Incorrect XML value: 'parse error at line 1 pos 11: unexpected END-OF-INPUT'

When the XPath value is invalid, it generates an Error 1105:

ERROR 1105 (HY000): XPATH syntax error: ')'

Explicit text() Expressions

This function is the equivalent of performing a match using the XPath expression after appending /text(). In other words:

SELECT
   EXTRACTVALUE('<cases><case>example</case></cases>', '/cases/case') AS 'Base Example',
   EXTRACTVALUE('<cases><case>example</case></cases>', '/cases/case/text()') AS 'text() Example';

+--------------+----------------+
| Base Example | text() Example |
+--------------+----------------+
| example      | example        |
+--------------+----------------+

Count Matches

When EXTRACTVALUE() returns multiple matches, it returns the content of the first child text node of each matching element, in the matched order, as a single, space-delimited string.

By design, the EXTRACTVALUE() function makes no distinction between a match on an empty element and no match at all. If you need to determine whether no matching element was found in the XML fragment or if an element was found that contained no child text nodes, use the XPath count() function.

For instance, when looking for a value that exists, but contains no child text nodes, you would get a count of the number of matching instances:

SELECT
   EXTRACTVALUE('<cases><case/></cases>', '/cases/case') AS 'Empty Example',
   EXTRACTVALUE('<cases><case/></cases>', 'count(/cases/case)') AS 'count() Example';

+---------------+-----------------+
| Empty Example | count() Example |
+---------------+-----------------+
|               |               1 |
+---------------+-----------------+

Alternatively, when looking for a value that doesn't exist, count() returns 0.

SELECT
   EXTRACTVALUE('<cases><case/></cases>', '/cases/person') AS 'No Match Example',
   EXTRACTVALUE('<cases><case/></cases>', 'count(/cases/person)') AS 'count() Example';

+------------------+-----------------+
| No Match Example | count() Example |
+------------------+-----------------+
|                  |                0|
+------------------+-----------------+

Matches

Important: The EXTRACTVALUE() function only returns CDDATA. It does not return tags that the element might contain or the text that these child elements contain.

SELECT EXTRACTVALUE('<cases><case>Person<email>x@example.com</email></case></cases>', '/cases') AS Case;

+--------+
| Case   |
+--------+
| Person |
+--------+

Note, in the above example, while the XPath expression matches to the parent <case> instance, it does not return the contained <email> tag or its content.

Examples

SELECT
    ExtractValue('<a>ccc<b>ddd</b></a>', '/a')            AS val1,
    ExtractValue('<a>ccc<b>ddd</b></a>', '/a/b')          AS val2,
    ExtractValue('<a>ccc<b>ddd</b></a>', '//b')           AS val3,
    ExtractValue('<a>ccc<b>ddd</b></a>', '/b')            AS val4,
    ExtractValue('<a>ccc<b>ddd</b><b>eee</b></a>', '//b') AS val5;
+------+------+------+------+---------+
| val1 | val2 | val3 | val4 | val5    |
+------+------+------+------+---------+
| ccc  | ddd  | ddd  |      | ddd eee |
+------+------+------+------+---------+

FIND_IN_SET

Syntax

FIND_IN_SET(pattern, strlist)

Description

Returns the index position where the given pattern occurs in a string list. The first argument is the pattern you want to search for. The second argument is a string containing comma-separated variables. If the second argument is of the SET data-type, the function is optimized to use bit arithmetic.

If the pattern does not occur in the string list or if the string list is an empty string, the function returns 0. If either argument is NULL, the function returns NULL. The function does not return the correct result if the pattern contains a comma (",") character.

Examples

SELECT FIND_IN_SET('b','a,b,c,d') AS "Found Results";
+---------------+
| Found Results |
+---------------+
|             2 |
+---------------+

See Also

  • ELT() function. Returns the N'th element from a set of strings.

FORMAT

Syntax

FORMAT(num, decimal_position[, locale])

Description

Formats the given number for display as a string, adding separators to appropriate position and rounding the results to the given decimal position. For instance, it would format 15233.345 to 15,233.35.

If the given decimal position is 0, it rounds to return no decimal point or fractional part. You can optionally specify a locale value to format numbers to the pattern appropriate for the given region.

Examples

SELECT FORMAT(1234567890.09876543210, 4) AS 'Format';
+--------------------+
| Format             |
+--------------------+
| 1,234,567,890.0988 |
+--------------------+

SELECT FORMAT(1234567.89, 4) AS 'Format';
+----------------+
| Format         |
+----------------+
| 1,234,567.8900 |
+----------------+

SELECT FORMAT(1234567.89, 0) AS 'Format';
+-----------+
| Format    |
+-----------+
| 1,234,568 |
+-----------+

SELECT FORMAT(123456789,2,'rm_CH') AS 'Format';
+----------------+
| Format         |
+----------------+
| 123'456'789,00 |
+----------------+

FROM_BASE64

Syntax

FROM_BASE64(str)

Description

Decodes the given base-64 encode string, returning the result as a binary string. Returns NULL if the given string is NULL or if it's invalid.

It is the reverse of the TO_BASE64 function.

There are numerous methods to base-64 encode a string. MariaDB uses the following:

  • It encodes alphabet value 64 as '+'.
  • It encodes alphabet value 63 as '/'.
  • It codes output in groups of four printable characters. Each three byte of data encoded uses four characters. If the final group is incomplete, it pads the difference with the '=' character.
  • It divides long output, adding a new line very 76 characters.
  • In decoding, it recognizes and ignores newlines, carriage returns, tabs and space whitespace characters.
SELECT TO_BASE64('Maria') AS 'Input';
+-----------+
| Input     |
+-----------+
| TWFyaWE=  |
+-----------+

SELECT FROM_BASE64('TWFyaWE=') AS 'Output';
+--------+
| Output |
+--------+
| Maria  |
+--------+

HEX

Syntax

HEX(N_or_S)

Description

If N_or_S is a number, returns a string representation of the hexadecimal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,16).

If N_or_S is a string, returns a hexadecimal string representation of N_or_S where each byte of each character in N_or_S is converted to two hexadecimal digits. If N_or_S is NULL, returns NULL. The inverse of this operation is performed by the UNHEX() function.


MariaDB starting with 10.5.0

HEX() with an INET6 argument returns a hexadecimal representation of the underlying 16-byte binary string.

Examples

SELECT HEX(255);
+----------+
| HEX(255) |
+----------+
| FF       |
+----------+

SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB          |
+------------------+

SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+

From MariaDB 10.5.0:

SELECT HEX(CAST('2001:db8::ff00:42:8329' AS INET6));
+----------------------------------------------+
| HEX(CAST('2001:db8::ff00:42:8329' AS INET6)) |
+----------------------------------------------+
| 20010DB8000000000000FF0000428329             |
+----------------------------------------------+

See Also

INSERT Function

Syntax

INSERT(str,pos,len,newstr)

Description

Returns the string str, with the substring beginning at position pos and len characters long replaced by the string newstr. Returns the original string if pos is not within the length of the string. Replaces the rest of the string from position pos if len is not within the length of the rest of the string. Returns NULL if any argument is NULL.

Examples

SELECT INSERT('Quadratic', 3, 4, 'What');
+-----------------------------------+
| INSERT('Quadratic', 3, 4, 'What') |
+-----------------------------------+
| QuWhattic                         |
+-----------------------------------+

SELECT INSERT('Quadratic', -1, 4, 'What');
+------------------------------------+
| INSERT('Quadratic', -1, 4, 'What') |
+------------------------------------+
| Quadratic                          |
+------------------------------------+

SELECT INSERT('Quadratic', 3, 100, 'What');
+-------------------------------------+
| INSERT('Quadratic', 3, 100, 'What') |
+-------------------------------------+
| QuWhat                              |
+-------------------------------------+

LENGTH

Syntax

LENGTH(str)

Description

Returns the length of the string str.

In the default mode, when Oracle mode from MariaDB 10.3 is not set, the length is measured in bytes. In this case, a multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

When running Oracle mode from MariaDB 10.3, the length is measured in characters, and LENGTH is a synonym for CHAR_LENGTH().

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

SELECT LENGTH('MariaDB');
+-------------------+
| LENGTH('MariaDB') |
+-------------------+
|                 7 |
+-------------------+

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

LOAD_FILE

Syntax

LOAD_FILE(file_name)

Description

Reads the file and returns the file contents as a string. To use this function, the file must be located on the server host, you must specify the full path name to the file, and you must have the FILE privilege. The file must be readable by all and it must be less than the size, in bytes, of the max_allowed_packet system variable. If the secure_file_priv system variable is set to a non-empty directory name, the file to be loaded must be located in that directory.

If the file does not exist or cannot be read because one of the preceding conditions is not satisfied, the function returns NULL.

Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings.

Statements using the LOAD_FILE() function are not safe for statement based replication. This is because the slave will execute the LOAD_FILE() command itself. If the file doesn't exist on the slave, the function will return NULL.

Examples

UPDATE t SET blob_col=LOAD_FILE('/tmp/picture') WHERE id=1;

See Also

LIKE

Syntax

expr LIKE pat [ESCAPE 'escape_char']
expr NOT LIKE pat [ESCAPE 'escape_char']

Description

Tests whether expr matches the pattern pat. Returns either 1 (TRUE) or 0 (FALSE). Both expr and pat may be any valid expression and are evaluated to strings. Patterns may use the following wildcard characters:

  • % matches any number of characters, including zero.
  • _ matches any single character.

Use NOT LIKE to test if a string does not match a pattern. This is equivalent to using the NOT operator on the entire LIKE expression.

If either the expression or the pattern is NULL, the result is NULL.

LIKE performs case-insensitive substring matches if the collation for the expression and pattern is case-insensitive. For case-sensitive matches, declare either argument to use a binary collation using COLLATE, or coerce either of them to a BINARY string using CAST. Use SHOW COLLATION to get a list of available collations. Collations ending in _bin are case-sensitive.

Numeric arguments are coerced to binary strings.

The _ wildcard matches a single character, not byte. It will only match a multi-byte character if it is valid in the expression's character set. For example, _ will match _utf8"€", but it will not match _latin1"€" because the Euro sign is not a valid latin1 character. If necessary, use CONVERT to use the expression in a different character set.

If you need to match the characters _ or %, you must escape them. By default, you can prefix the wildcard characters the backslash character \ to escape them. The backslash is used both to encode special characters like newlines when a string is parsed as well as to escape wildcards in a pattern after parsing. Thus, to match an actual backslash, you sometimes need to double-escape it as "\\\\".

To avoid difficulties with the backslash character, you can change the wildcard escape character using ESCAPE in a LIKE expression. The argument to ESCAPE must be a single-character string.

Examples

Select the days that begin with "T":

CREATE TABLE t1 (d VARCHAR(16));
INSERT INTO t1 VALUES ("Monday"), ("Tuesday"), ("Wednesday"), ("Thursday"), ("Friday"), ("Saturday"), ("Sunday");
SELECT * FROM t1 WHERE d LIKE "T%";
SELECT * FROM t1 WHERE d LIKE "T%";
+----------+
| d        |
+----------+
| Tuesday  |
| Thursday |
+----------+

Select the days that contain the substring "es":

SELECT * FROM t1 WHERE d LIKE "%es%";
SELECT * FROM t1 WHERE d LIKE "%es%";
+-----------+
| d         |
+-----------+
| Tuesday   |
| Wednesday |
+-----------+

Select the six-character day names:

SELECT * FROM t1 WHERE d like "___day";
SELECT * FROM t1 WHERE d like "___day";
+---------+
| d       |
+---------+
| Monday  |
| Friday  |
| Sunday  |
+---------+

With the default collations, LIKE is case-insensitive:

SELECT * FROM t1 where d like "t%";
SELECT * FROM t1 where d like "t%";
+----------+
| d        |
+----------+
| Tuesday  |
| Thursday |
+----------+

Use COLLATE to specify a binary collation, forcing case-sensitive matches:

SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;
SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;
Empty set (0.00 sec)

You can include functions and operators in the expression to match. Select dates based on their day name:

CREATE TABLE t2 (d DATETIME);
INSERT INTO t2 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";
SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";
+------------------+
| d                |
+------------------+
| 2007-01-30 21:31 |
| 2011-04-21 12:34 |
| 2004-10-07 11:19 |
+------------------+
3 rows in set, 7 warnings (0.00 sec)

Optimizing LIKE

  • MariaDB can use indexes for LIKE on string columns in the case where the LIKE doesn't start with % or _.
  • Starting from MariaDB 10.0, one can set the optimizer_use_condition_selectivity variable to 5. If this is done, then the optimizer will read optimizer_selectivity_sampling_limit rows to calculate the selectivity of the LIKE expression before starting to calculate the query plan. This can help speed up some LIKE queries by providing the optimizer with more information about your data.

See Also

LOCATE

Syntax

LOCATE(substr,str), LOCATE(substr,str,pos)

Description

The first syntax returns the position of the first occurrence of substring substr in string str. The second syntax returns the position of the first occurrence of substring substr in string str, starting at position pos. Returns 0 if substr is not in str.

LOCATE() performs a case-insensitive search.

If any argument is NULL, returns NULL.

INSTR() is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed.

Examples

SELECT LOCATE('bar', 'foobarbar');
+----------------------------+
| LOCATE('bar', 'foobarbar') |
+----------------------------+
|                          4 |
+----------------------------+

SELECT LOCATE('My', 'Maria');
+-----------------------+
| LOCATE('My', 'Maria') |
+-----------------------+
|                     0 |
+-----------------------+

SELECT LOCATE('bar', 'foobarbar', 5);
+-------------------------------+
| LOCATE('bar', 'foobarbar', 5) |
+-------------------------------+
|                             7 |
+-------------------------------+

See Also

  • INSTR() ; Returns the position of a string withing a string
  • SUBSTRING_INDEX() ; Returns the substring from string before count occurrences of a delimiter

LOWER

Syntax

LOWER(str)

Description

Returns the string str with all characters changed to lowercase according to the current character set mapping. The default is latin1 (cp1252 West European).

Examples

 SELECT LOWER('QUADRATICALLY');
+------------------------+
| LOWER('QUADRATICALLY') |
+------------------------+
| quadratically          |
+------------------------+

LOWER() (and UPPER()) are ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). To perform lettercase conversion, CONVERT the string to a non-binary string:

SET @str = BINARY 'North Carolina';

SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
+----------------+-----------------------------------+
| LOWER(@str)    | LOWER(CONVERT(@str USING latin1)) |
+----------------+-----------------------------------+
| North Carolina | north carolina                    |
+----------------+-----------------------------------+

LPAD

Syntax

LPAD(str, len [,padstr])

Description

Returns the string str, left-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the LPAD function pads spaces.

Prior to MariaDB 10.3.1, the padstr parameter was mandatory.

Returns NULL if given a NULL argument. If the result is empty (zero length), returns either an empty string or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using LPAD_ORACLE as the function name.

Examples

SELECT LPAD('hello',10,'.');
+----------------------+
| LPAD('hello',10,'.') |
+----------------------+
| .....hello           |
+----------------------+

SELECT LPAD('hello',2,'.');
+---------------------+
| LPAD('hello',2,'.') |
+---------------------+
| he                  |
+---------------------+

From MariaDB 10.3.1, with the pad string defaulting to space.

SELECT LPAD('hello',10);
+------------------+
| LPAD('hello',10) |
+------------------+
|      hello       |
+------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT LPAD('',0),LPAD_ORACLE('',0);
+------------+-------------------+
| LPAD('',0) | LPAD_ORACLE('',0) |
+------------+-------------------+
|            | NULL              |
+------------+-------------------+

See Also

  • RPAD - Right-padding instead of left-padding.

LTRIM

Syntax

LTRIM(str)

Description

Returns the string str with leading space characters removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using LTRIM_ORACLE as the function name.

Examples

SELECT QUOTE(LTRIM('   MariaDB   '));
+-------------------------------+
| QUOTE(LTRIM('   MariaDB   ')) |
+-------------------------------+
| 'MariaDB   '                  |
+-------------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT LTRIM(''),LTRIM_ORACLE('');
+-----------+------------------+
| LTRIM('') | LTRIM_ORACLE('') |
+-----------+------------------+
|           | NULL             |
+-----------+------------------+

See Also

  • RTRIM - trailing spaces removed
  • TRIM - removes all given prefixes or suffixes

MAKE_SET

Syntax

MAKE_SET(bits,str1,str2,...)

Description

Returns a set value (a string containing substrings separated by "," characters) consisting of the strings that have the corresponding bit in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL values in str1, str2, ... are not appended to the result.

Examples

SELECT MAKE_SET(1,'a','b','c');
+-------------------------+
| MAKE_SET(1,'a','b','c') |
+-------------------------+
| a                       |
+-------------------------+

SELECT MAKE_SET(1 | 4,'hello','nice','world');
+----------------------------------------+
| MAKE_SET(1 | 4,'hello','nice','world') |
+----------------------------------------+
| hello,world                            |
+----------------------------------------+

SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world');
+---------------------------------------------+
| MAKE_SET(1 | 4,'hello','nice',NULL,'world') |
+---------------------------------------------+
| hello                                       |
+---------------------------------------------+

SELECT QUOTE(MAKE_SET(0,'a','b','c'));
+--------------------------------+
| QUOTE(MAKE_SET(0,'a','b','c')) |
+--------------------------------+
| ''                             |
+--------------------------------+

MATCH AGAINST

Syntax

MATCH (col1,col2,...) AGAINST (expr [search_modifier])

Description

A special construct used to perform a fulltext search on a fulltext index.

See Fulltext Index Overview for a full description, and Full-text Indexes for more articles on the topic.

Examples

CREATE TABLE ft_myisam(copy TEXT,FULLTEXT(copy)) ENGINE=MyISAM;

INSERT INTO ft_myisam(copy) VALUES ('Once upon a time'), ('There was a wicked witch'), 
 ('Who ate everybody up');

SELECT * FROM ft_myisam WHERE MATCH(copy) AGAINST('wicked');
+--------------------------+
| copy                     |
+--------------------------+
| There was a wicked witch |
+--------------------------+
SELECT id, body, MATCH (title,body) AGAINST
    ('Security implications of running MySQL as root'
    IN NATURAL LANGUAGE MODE) AS score
    FROM articles WHERE MATCH (title,body) AGAINST
    ('Security implications of running MySQL as root'
    IN NATURAL LANGUAGE MODE);
+----+-------------------------------------+-----------------+
| id | body                                | score           |
+----+-------------------------------------+-----------------+
|  4 | 1. Never run mysqld as root. 2. ... | 1.5219271183014 |
|  6 | When configured properly, MySQL ... | 1.3114095926285 |
+----+-------------------------------------+-----------------+

REGEXP_INSTR

MariaDB starting with 10.0.5

REGEXP_INSTR was introduced in MariaDB 10.0.5.

Syntax

REGEXP_INSTR(subject, pattern)

Returns the position of the first occurrence of the regular expression pattern in the string subject, or 0 if pattern was not found.

The positions start with 1 and are measured in characters (i.e. not in bytes), which is important for multi-byte character sets. You can cast a multi-byte character set to BINARY to get offsets in bytes.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_INSTR was introduced as part of this enhancement.

Examples

SELECT REGEXP_INSTR('abc','b');
-> 2

SELECT REGEXP_INSTR('abc','x');
-> 0

SELECT REGEXP_INSTR('BJÖRN','N');
-> 5

Casting a multi-byte character set as BINARY to get offsets in bytes:

SELECT REGEXP_INSTR(BINARY 'BJÖRN','N') AS cast_utf8_to_binary;
-> 6

Case sensitivity:

SELECT REGEXP_INSTR('ABC','b');
-> 2

SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'b');
-> 0

SELECT REGEXP_INSTR(BINARY'ABC','b');
-> 0

SELECT REGEXP_INSTR('ABC','(?-i)b');
-> 0

SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'(?i)b');
-> 2

REGEXP_REPLACE

MariaDB starting with 10.0.5

REGEXP_REPLACE was introduced in MariaDB 10.0.5.

Syntax

REGEXP_REPLACE(subject, pattern, replace)

Description

REGEXP_REPLACE returns the string subject with all occurrences of the regular expression pattern replaced by the string replace. If no occurrences are found, then subject is returned as is.

The replace string can have backreferences to the subexpressions in the form \N, where N is a number from 1 to 9.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_REPLACE was introduced as part of this enhancement.

MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library.

Examples

SELECT REGEXP_REPLACE('ab12cd','[0-9]','') AS remove_digits;
-> abcd

SELECT REGEXP_REPLACE('<html><head><title>title</title><body>body</body></htm>', '<.+?>',' ')
AS strip_html;
-> title  body

Backreferences to the subexpressions in the form \N, where N is a number from 1 to 9:

SELECT REGEXP_REPLACE('James Bond','^(.*) (.*)$','\\2, \\1') AS reorder_name;
-> Bond, James

Case insensitive and case sensitive matches:

SELECT REGEXP_REPLACE('ABC','b','-') AS case_insensitive;
-> A-C

SELECT REGEXP_REPLACE('ABC' COLLATE utf8_bin,'b','-') AS case_sensitive;
-> ABC

SELECT REGEXP_REPLACE(BINARY 'ABC','b','-') AS binary_data;
-> ABC

Overwriting the collation case sensitivity using the (?i) and (?-i) PCRE flags.

SELECT REGEXP_REPLACE('ABC','(?-i)b','-') AS force_case_sensitive;
-> ABC

SELECT REGEXP_REPLACE(BINARY 'ABC','(?i)b','-') AS force_case_insensitive;
-> A-C

REGEXP_SUBSTR

MariaDB starting with 10.0.5

REGEXP_SUBSTR was introduced in MariaDB 10.0.5.

Syntax

REGEXP_SUBSTR(subject,pattern)

Description

Returns the part of the string subject that matches the regular expression pattern, or an empty string if pattern was not found.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB 10.0.5 switched to the PCRE regular expression library for enhanced regular expression performance, and REGEXP_SUBSTR was introduced as part of this enhancement.

MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library.

Examples

SELECT REGEXP_SUBSTR('ab12cd','[0-9]+');
-> 12

SELECT REGEXP_SUBSTR(
  'See https://mariadb.org/en/foundation/ for details',
  'https?://[^/]*');
-> https://mariadb.org
SELECT REGEXP_SUBSTR('ABC','b');
-> B

SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'b');
->

SELECT REGEXP_SUBSTR(BINARY'ABC','b');
->

SELECT REGEXP_SUBSTR('ABC','(?i)b');
-> B

SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'(?+i)b');
-> B

RPAD

Syntax

RPAD(str, len [, padstr])

Description

Returns the string str, right-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the RPAD function pads spaces.

Prior to MariaDB 10.3.1, the padstr parameter was mandatory.

Returns NULL if given a NULL argument. If the result is empty (a length of zero), returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using RPAD_ORACLE as the function name.

Examples

SELECT RPAD('hello',10,'.');
+----------------------+
| RPAD('hello',10,'.') |
+----------------------+
| hello.....           |
+----------------------+

SELECT RPAD('hello',2,'.');
+---------------------+
| RPAD('hello',2,'.') |
+---------------------+
| he                  |
+---------------------+

From MariaDB 10.3.1, with the pad string defaulting to space.

SELECT RPAD('hello',30);
+--------------------------------+
| RPAD('hello',30)               |
+--------------------------------+
| hello                          |
+--------------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT RPAD('',0),RPAD_ORACLE('',0);
+------------+-------------------+
| RPAD('',0) | RPAD_ORACLE('',0) |
+------------+-------------------+
|            | NULL              |
+------------+-------------------+

See Also

  • LPAD - Left-padding instead of right-padding.

RTRIM

Syntax

RTRIM(str)

Description

Returns the string str with trailing space characters removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using RTRIM_ORACLE as the function name.

Examples

SELECT QUOTE(RTRIM('MariaDB    '));
+-----------------------------+
| QUOTE(RTRIM('MariaDB    ')) |
+-----------------------------+
| 'MariaDB'                   |
+-----------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT RTRIM(''),RTRIM_ORACLE('');
+-----------+------------------+
| RTRIM('') | RTRIM_ORACLE('') |
+-----------+------------------+
|           | NULL             |
+-----------+------------------+

See Also

  • LTRIM - leading spaces removed
  • TRIM - removes all given prefixes or suffixes

SOUNDEX

Syntax

SOUNDEX(str)

Description

Returns a soundex string from str. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the SOUNDEX() function returns an arbitrarily long string. You can use SUBSTRING() on the result to get a standard soundex string. All non-alphabetic characters in str are ignored. All international alphabetic characters outside the A-Z range are treated as vowels.

Important: When using SOUNDEX(), you should be aware of the following details:

  • This function, as currently implemented, is intended to work well with strings that are in the English language only. Strings in other languages may not produce reasonable results.
  • This function implements the original Soundex algorithm, not the more popular enhanced version (also described by D. Knuth). The difference is that original version discards vowels first and duplicates second, whereas the enhanced version discards duplicates first and vowels second.

Examples

SOUNDEX('Hello');
+------------------+
| SOUNDEX('Hello') |
+------------------+
| H400             |
+------------------+
SELECT SOUNDEX('MariaDB');
+--------------------+
| SOUNDEX('MariaDB') |
+--------------------+
| M631               |
+--------------------+
SELECT SOUNDEX('Knowledgebase');
+--------------------------+
| SOUNDEX('Knowledgebase') |
+--------------------------+
| K543212                  |
+--------------------------+
SELECT givenname, surname FROM users WHERE SOUNDEX(givenname) = SOUNDEX("robert");
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto   | Castro  |
+-----------+---------+

See Also

SUBSTRING

Syntax

SUBSTRING(str,pos), 
SUBSTRING(str FROM pos), 
SUBSTRING(str,pos,len),
SUBSTRING(str FROM pos FOR len)

SUBSTR(str,pos), 
SUBSTR(str FROM pos), 
SUBSTR(str,pos,len),
SUBSTR(str FROM pos FOR len)

Description

The forms without a len argument return a substring from string str starting at position pos.

The forms with a len argument return a substring len characters long from string str, starting at position pos.

The forms that use FROM are standard SQL syntax.

It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning. A negative value may be used for pos in any of the forms of this function.

By default, the position of the first character in the string from which the substring is to be extracted is reckoned as 1. For Oracle-compatibility, from MariaDB 10.3.3, when sql_mode is set to 'oracle', position zero is treated as position 1 (although the first character is still reckoned as 1).

If any argument is NULL, returns NULL.

Examples

SELECT SUBSTRING('Knowledgebase',5);
+------------------------------+
| SUBSTRING('Knowledgebase',5) |
+------------------------------+
| ledgebase                    |
+------------------------------+

SELECT SUBSTRING('MariaDB' FROM 6);
+-----------------------------+
| SUBSTRING('MariaDB' FROM 6) |
+-----------------------------+
| DB                          |
+-----------------------------+

SELECT SUBSTRING('Knowledgebase',3,7);
+--------------------------------+
| SUBSTRING('Knowledgebase',3,7) |
+--------------------------------+
| owledge                        |
+--------------------------------+

SELECT SUBSTRING('Knowledgebase', -4);
+--------------------------------+
| SUBSTRING('Knowledgebase', -4) |
+--------------------------------+
| base                           |
+--------------------------------+

SELECT SUBSTRING('Knowledgebase', -8, 4);
+-----------------------------------+
| SUBSTRING('Knowledgebase', -8, 4) |
+-----------------------------------+
| edge                              |
+-----------------------------------+

SELECT SUBSTRING('Knowledgebase' FROM -8 FOR 4);
+------------------------------------------+
| SUBSTRING('Knowledgebase' FROM -8 FOR 4) |
+------------------------------------------+
| edge                                     |
+------------------------------------------+

Oracle mode from MariaDB 10.3.3:

SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
|                   |
+-------------------+

SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab                |
+-------------------+

SET sql_mode='oracle';

SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
| abc               |
+-------------------+

SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab                |
+-------------------+

See Also

  • INSTR() - Returns the position of a string within a string
  • LOCATE() - Returns the position of a string within a string
  • SUBSTRING_INDEX() - Returns a string based on substring

SUBSTRING_INDEX

Syntax

SUBSTRING_INDEX(str,delim,count)

Description

Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.

If any argument is NULL, returns NULL.

For example

SUBSTRING_INDEX('www.mariadb.org', '.', 2)

means "Return all of the characters up to the 2nd occurrence of ."

Examples

SELECT SUBSTRING_INDEX('www.mariadb.org', '.', 2);
+--------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', 2) |
+--------------------------------------------+
| www.mariadb                                |
+--------------------------------------------+

SELECT SUBSTRING_INDEX('www.mariadb.org', '.', -2);
+---------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', -2) |
+---------------------------------------------+
| mariadb.org                                 |
+---------------------------------------------+

See Also

  • INSTR() - Returns the position of a string within a string
  • LOCATE() - Returns the position of a string within a string
  • SUBSTRING() - Returns a string based on position

TO_BASE64

MariaDB starting with 10.0.5

The TO_BASE64() function was introduced in MariaDB 10.0.5.

Syntax

TO_BASE64(str)

Description

Converts the string argument str to its base-64 encoded form, returning the result as a character string in the connection character set and collation.

The argument str will be converted to string first if it is not a string. A NULL argument will return a NULL result.

The reverse function, FROM_BASE64(), decodes an encoded base-64 string.

There are a numerous different methods to base-64 encode a string. The following are used by MariaDB and MySQL:

  • Alphabet value 64 is encoded as '+'.
  • Alphabet value 63 is encoded as '/'.
  • Encoding output is made up of groups of four printable characters, with each three bytes of data encoded using four characters. If the final group is not complete, it is padded with '=' characters to make up a length of four.
  • To divide long output, a newline is added after every 76 characters.
  • Decoding will recognize and ignore newlines, carriage returns, tabs, and spaces.

Examples

SELECT TO_BASE64('Maria');
+--------------------+
| TO_BASE64('Maria') |
+--------------------+
| TWFyaWE=           |
+--------------------+

TRIM

Syntax

TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)

From MariaDB 10.3.6

TRIM_ORACLE([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)

Description

Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr is optional and, if not specified, spaces are removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. SQL_MODE=Oracle is not set by default.

The Oracle mode version of the function can be accessed in any mode by using TRIM_ORACLE as the function name.

Examples

SELECT TRIM('  bar   ')\G
*************************** 1. row ***************************
TRIM('  bar   '): bar

SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx')\G
*************************** 1. row ***************************
TRIM(LEADING 'x' FROM 'xxxbarxxx'): barxxx

SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx')\G
*************************** 1. row ***************************
TRIM(BOTH 'x' FROM 'xxxbarxxx'): bar

SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz')\G
*************************** 1. row ***************************
TRIM(TRAILING 'xyz' FROM 'barxxyz'): barx

From MariaDB 10.3.6, with SQL_MODE=Oracle not set:

SELECT TRIM(''),TRIM_ORACLE('');
+----------+-----------------+
| TRIM('') | TRIM_ORACLE('') |
+----------+-----------------+
|          | NULL            |
+----------+-----------------+

From MariaDB 10.3.6, with SQL_MODE=Oracle set:

SELECT TRIM(''),TRIM_ORACLE('');
+----------+-----------------+
| TRIM('') | TRIM_ORACLE('') |
+----------+-----------------+
| NULL     | NULL            |
+----------+-----------------+

See Also

  • LTRIM - leading spaces removed
  • RTRIM - trailing spaces removed

UNHEX

Syntax

UNHEX(str)

Description

Performs the inverse operation of HEX(str). That is, it interprets each pair of hexadecimal digits in the argument as a number and converts it to the character represented by the number. The resulting characters are returned as a binary string.

If str is NULL, UNHEX() returns NULL.

Examples

SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+

SELECT UNHEX('4D617269614442');
+-------------------------+
| UNHEX('4D617269614442') |
+-------------------------+
| MariaDB                 |
+-------------------------+

SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB          |
+------------------+

SELECT UNHEX(HEX('string'));
+----------------------+
| UNHEX(HEX('string')) |
+----------------------+
| string               |
+----------------------+

SELECT HEX(UNHEX('1267'));
+--------------------+
| HEX(UNHEX('1267')) |
+--------------------+
| 1267               |
+--------------------+

See Also

UPDATEXML

Syntax

UpdateXML(xml_target, xpath_expr, new_xml)

Description

This function replaces a single portion of a given fragment of XML markup xml_target with a new XML fragment new_xml, and then returns the changed XML. The portion of xml_target that is replaced matches an XPath expression xpath_expr supplied by the user. If no expression matching xpath_expr is found, or if multiple matches are found, the function returns the original xml_target XML fragment. All three arguments should be strings.

Examples

SELECT
    UpdateXML('<a><b>ccc</b><d></d></a>', '/a', '<e>fff</e>') AS val1,
    UpdateXML('<a><b>ccc</b><d></d></a>', '/b', '<e>fff</e>') AS val2,
    UpdateXML('<a><b>ccc</b><d></d></a>', '//b', '<e>fff</e>') AS val3,
    UpdateXML('<a><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val4,
    UpdateXML('<a><d></d><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val5
    \G
*************************** 1. row ***************************
val1: <e>fff</e>
val2: <a><b>ccc</b><d></d></a>
val3: <a><e>fff</e><d></d></a>
val4: <a><b>ccc</b><e>fff</e></a>
val5: <a><d></d><b>ccc</b><d></d></a>
1 row in set (0.00 sec)

WEIGHT_STRING

MariaDB starting with 10.0.5

The WEIGHT_STRING function was introduced in MariaDB 10.0.5.

Syntax

WEIGHT_STRING(str [AS {CHAR|BINARY}(N)] [LEVEL levels] [flags])
  levels: N [ASC|DESC|REVERSE] [, N [ASC|DESC|REVERSE]] ... 

Description

Returns a binary string representing the string's sorting and comparison value. A string with a lower result means that for sorting purposes the string appears before a string with a higher result.

WEIGHT_STRING() is particularly useful when adding new collations, for testing purposes.

If str is a non-binary string (CHAR, VARCHAR or TEXT), WEIGHT_STRING returns the string's collation weight. If str is a binary string (BINARY, VARBINARY or BLOB), the return value is simply the input value, since the weight for each byte in a binary string is the byte value.

WEIGHT_STRING() returns NULL if given a NULL input.

The optional AS clause permits casting the input string to a binary or non-binary string, as well as to a particular length.

AS BINARY(N) measures the length in bytes rather than characters, and right pads with 0x00 bytes to the desired length.

AS CHAR(N) measures the length in characters, and right pads with spaces to the desired length.

N has a minimum value of 1, and if it is less than the length of the input string, the string is truncated without warning.

The optional LEVEL clause specifies that the return value should contain weights for specific collation levels. The levels specifier can either be a single integer, a comma-separated list of integers, or a range of integers separated by a dash (whitespace is ignored). Integers can range from 1 to a maximum of 6, dependent on the collation, and need to be listed in ascending order.

If the LEVEL clause is no provided, a default of 1 to the maximum for the collation is assumed.

If the LEVEL is specified without using a range, an optional modifier is permitted.

ASC, the default, returns the weights without any modification.

DESC returns bitwise-inverted weights.

REVERSE returns the weights in reverse order.

Examples

The examples below use the HEX() function to represent non-printable results in hexadecimal format.

SELECT HEX(WEIGHT_STRING('x'));
+-------------------------+
| HEX(WEIGHT_STRING('x')) |
+-------------------------+
| 0058                    |
+-------------------------+

SELECT HEX(WEIGHT_STRING('x' AS BINARY(4)));
+--------------------------------------+
| HEX(WEIGHT_STRING('x' AS BINARY(4))) |
+--------------------------------------+
| 78000000                             |
+--------------------------------------+

SELECT HEX(WEIGHT_STRING('x' AS CHAR(4)));
+------------------------------------+
| HEX(WEIGHT_STRING('x' AS CHAR(4))) |
+------------------------------------+
| 0058002000200020                   |
+------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1));
+--------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1)) |
+--------------------------------------+
| AA22EE                               |
+--------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC));
+-------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC)) |
+-------------------------------------------+
| 55DD11                                    |
+-------------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE));
+----------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE)) |
+----------------------------------------------+
| EE22AA                                       |
+----------------------------------------------+

CREATE DATABASE

Syntax

CREATE [OR REPLACE] {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_specification] ...

create_specification:
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'comment'

Description

CREATE DATABASE creates a database with the given name. To use this statement, you need the CREATE privilege for the database. CREATE SCHEMA is a synonym for CREATE DATABASE.

For valid identifiers to use as database names, see Identifier Names.

OR REPLACE

MariaDB starting with 10.1.3

The OR REPLACE clause was added in MariaDB 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP DATABASE IF EXISTS db_name;
CREATE DATABASE db_name ...;

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified database already exists.

COMMENT

MariaDB starting with 10.5.0

From MariaDB 10.5.0, it is possible to add a comment of a maximum of 1024 bytes. If the comment length exceeds this length, a error/warning code 4144 is thrown. The database comment is also added to the db.opt file, as well as to the information_schema.schemata table.

Examples

CREATE DATABASE db1;
Query OK, 1 row affected (0.18 sec)

CREATE DATABASE db1;
ERROR 1007 (HY000): Can't create database 'db1'; database exists

CREATE OR REPLACE DATABASE db1;
Query OK, 2 rows affected (0.00 sec)

CREATE DATABASE IF NOT EXISTS db1;
Query OK, 1 row affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------+
| Level | Code | Message                                      |
+-------+------+----------------------------------------------+
| Note  | 1007 | Can't create database 'db1'; database exists |
+-------+------+----------------------------------------------+

Setting the character sets and collation. See Setting Character Sets and Collations for more details.

CREATE DATABASE czech_slovak_names 
  CHARACTER SET = 'keybcs2'
  COLLATE = 'keybcs2_bin';

Comments, from MariaDB 10.5.0:

CREATE DATABASE presentations COMMENT 'Presentations for conferences';

See Also

CONSTRAINT

MariaDB supports the implementation of constraints at the table-level using either CREATE TABLE or ALTER TABLE statements. A table constraint restricts the data you can add to the table. If you attempt to insert invalid data on a column, MariaDB throws an error.

Syntax

[CONSTRAINT [symbol]] constraint_expression

constraint_expression:
  | PRIMARY KEY [index_type] (index_col_name, ...) [index_option] ...
  | FOREIGN KEY [index_name] (index_col_name, ...) 
       REFERENCES tbl_name (index_col_name, ...)
       [ON DELETE reference_option]
       [ON UPDATE reference_option]
  | UNIQUE [INDEX|KEY] [index_name]
       [index_type] (index_col_name, ...) [index_option] ...
  | CHECK (check_constraints)

index_type:
  USING {BTREE | HASH | RTREE}

index_col_name:
  col_name [(length)] [ASC | DESC]

index_option:
  | KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES|NO}

reference_option:
  RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT

Description

Constraints provide restrictions on the data you can add to a table. This allows you to enforce data integrity from MariaDB, rather than through application logic. When a statement violates a constraint, MariaDB throws an error.

There are four types of table constraints:

ConstraintDescription
PRIMARY KEYSets the column for referencing rows. Values must be unique and not null.
FOREIGN KEYSets the column to reference the primary key on another table.
UNIQUERequires values in column or columns only occur once in the table.
CHECKChecks whether the data meets the given condition.

The Information Schema TABLE_CONSTRAINTS Table contains information about tables that have constraints.

FOREIGN KEY Constraints

InnoDB supports foreign key constraints. The syntax for a foreign key constraint definition in InnoDB looks like this:

[CONSTRAINT [symbol]] FOREIGN KEY
    [index_name] (index_col_name, ...)
    REFERENCES tbl_name (index_col_name,...)
    [ON DELETE reference_option]
    [ON UPDATE reference_option]

reference_option:
    RESTRICT | CASCADE | SET NULL | NO ACTION

The Information Schema REFERENTIAL_CONSTRAINTS table has more information about foreign keys.

CHECK Constraints

MariaDB starting with 10.2.1

From MariaDB 10.2.1, constraints are enforced. Before MariaDB 10.2.1 constraint expressions were accepted in the syntax but ignored.

In MariaDB 10.2.1 you can define constraints in 2 different ways:

  • CHECK(expression) given as part of a column definition.
  • CONSTRAINT [constraint_name] CHECK (expression)

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint expression returns false, then the row will not be inserted or updated. One can use most deterministic functions in a constraint, including UDFs.

CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b));

If you use the second format and you don't give a name to the constraint, then the constraint will get an automatically generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name.

One can disable all constraint expression checks by setting the check_constraint_checks variable to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL.

Replication

In row-based replication, only the master checks constraints, and failed statements will not be replicated. In statement-based replication, the slaves will also check constraints. Constraints should therefore be identical, as well as deterministic, in a replication environment.

Auto_increment

MariaDB starting with 10.2.6

Examples

CREATE TABLE product (category INT NOT NULL, id INT NOT NULL,
                      price DECIMAL,
                      PRIMARY KEY(category, id)) ENGINE=INNODB;
CREATE TABLE customer (id INT NOT NULL,
                       PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT,
                            product_category INT NOT NULL,
                            product_id INT NOT NULL,
                            customer_id INT NOT NULL,
                            PRIMARY KEY(no),
                            INDEX (product_category, product_id),
                            FOREIGN KEY (product_category, product_id)
                              REFERENCES product(category, id)
                              ON UPDATE CASCADE ON DELETE RESTRICT,
                            INDEX (customer_id),
                            FOREIGN KEY (customer_id)
                              REFERENCES customer(id)) ENGINE=INNODB;
MariaDB starting with 10.2.1

The following examples will work from MariaDB 10.2.1 onwards.

Numeric constraints and comparisons:

CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b));

INSERT INTO t1(a) VALUES (1);
ERROR 4022 (23000): CONSTRAINT `a` failed for `test`.`t1`

INSERT INTO t1(a,b) VALUES (3,4);
ERROR 4022 (23000): CONSTRAINT `a_greater` failed for `test`.`t1`

INSERT INTO t1(a,b) VALUES (4,3);
Query OK, 1 row affected (0.04 sec)

Dropping a constraint:

ALTER TABLE t1 DROP CONSTRAINT a_greater;

Adding a constraint:

ALTER TABLE t1 ADD CONSTRAINT a_greater CHECK (a>b);

Date comparisons and character length:

CREATE TABLE t2 (name VARCHAR(30) CHECK (CHAR_LENGTH(name)>2), start_date DATE, 
  end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date<end_date));

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', '2003-12-15', '2014-11-09');
Query OK, 1 row affected (0.04 sec)

INSERT INTO t2(name, start_date, end_date) VALUES('Io', '2003-12-15', '2014-11-09');
ERROR 4022 (23000): CONSTRAINT `name` failed for `test`.`t2`

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', NULL, '2014-11-09');
Query OK, 1 row affected (0.04 sec)

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', '2015-12-15', '2014-11-09');
ERROR 4022 (23000): CONSTRAINT `end_date` failed for `test`.`t2`

A misplaced parenthesis:

CREATE TABLE t3 (name VARCHAR(30) CHECK (CHAR_LENGTH(name>2)), start_date DATE, 
  end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date<end_date));
Query OK, 0 rows affected (0.32 sec)

INSERT INTO t3(name, start_date, end_date) VALUES('Io', '2003-12-15', '2014-11-09');
Query OK, 1 row affected, 1 warning (0.04 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'Io' |
+---------+------+----------------------------------------+

Compare the definition of table t2 to table t3. CHAR_LENGTH(name)>2 is very different to CHAR_LENGTH(name>2) as the latter mistakenly performs a numeric comparison on the name field, leading to unexpected results.

See Also

CREATE EVENT

Syntax

CREATE [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    EVENT 
    [IF NOT EXISTS]
    event_name    
    ON SCHEDULE schedule
    [ON COMPLETION [NOT] PRESERVE]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    DO sql_statement;

schedule:
    AT timestamp [+ INTERVAL interval] ...
  | EVERY interval 
    [STARTS timestamp [+ INTERVAL interval] ...] 
    [ENDS timestamp [+ INTERVAL interval] ...]

interval:
    quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
              WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
              DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}

Description

This statement creates and schedules a new event. It requires the EVENT privilege for the schema in which the event is to be created.

The minimum requirements for a valid CREATE EVENT statement are as follows:

  • The keywords CREATE EVENT plus an event name, which uniquely identifies the event in the current schema. (Prior to MySQL 5.1.12, the event name needed to be unique only among events created by the same user on a given database.)
  • An ON SCHEDULE clause, which determines when and how often the event executes.
  • A DO clause, which contains the SQL statement to be executed by an event.

Here is an example of a minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

The previous statement creates an event named myevent. This event executes once one hour following its creation by running an SQL statement that increments the value of the myschema.mytable table's mycol column by 1.

The event_name must be a valid MariaDB identifier with a maximum length of 64 characters. It may be delimited using back ticks, and may be qualified with the name of a database schema. An event is associated with both a MariaDB user (the definer) and a schema, and its name must be unique among names of events within that schema. In general, the rules governing event names are the same as those for names of stored routines. See Identifier Names.

If no schema is indicated as part of event_name, the default (current) schema is assumed.

For valid identifiers to use as event names, see Identifier Names.

OR REPLACE

The OR REPLACE clause was included in MariaDB 10.1.4. If used and the event already exists, instead of an error being returned, the existing event will be dropped and replaced by the newly defined event.

IF NOT EXISTS

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the event already exists. Cannot be used together with OR REPLACE.

ON SCHEDULE

The ON SCHEDULE clause can be used to specify when the event must be triggered.

AT

If you want to execute the event only once (one time event), you can use the AT keyword, followed by a timestamp. If you use CURRENT_TIMESTAMP, the event acts as soon as it is created. As a convenience, you can add one or more intervals to that timestamp. You can also specify a timestamp in the past, so that the event is stored but not triggered, until you modify it via ALTER EVENT.

The following example shows how to create an event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

You can also specify that an event must be triggered at a regular interval (recurring event). In such cases, use the EVERY clause followed by the interval.

If an event is recurring, you can specify when the first execution must happen via the STARTS clause and a maximum time for the last execution via the ENDS clause. STARTS and ENDS clauses are followed by a timestamp and, optionally, one or more intervals. The ENDS clause can specify a timestamp in the past, so that the event is stored but not executed until you modify it via ALTER EVENT.

In the following example, next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

Intervals consist of a quantity and a time unit. The time units are the same used for other staments and time functions, except that you can't use microseconds for events. For simple time units, like HOUR or MINUTE, the quantity is an integer number, for example '10 MINUTE'. For composite time units, like HOUR_MINUTE or HOUR_SECOND, the quantity must be a string with all involved simple values and their separators, for example '2:30' or '2:30:30'.

ON COMPLETION [NOT] PRESERVE

The ON COMPLETION clause can be used to specify if the event must be deleted after its last execution (that is, after its AT or ENDS timestamp is past). By default, events are dropped when they are expired. To explicitly state that this is the desired behaviour, you can use ON COMPLETION NOT PRESERVE. Instead, if you want the event to be preserved, you can use ON COMPLETION PRESERVE.

In you specify ON COMPLETION NOT PRESERVE, and you specify a timestamp in the past for AT or ENDS clause, the event will be immediatly dropped. In such cases, you will get a Note 1558: "Event execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation".

ENABLE/DISABLE/DISABLE ON SLAVE

Events are ENABLEd by default. If you want to stop MariaDB from executing an event, you may specify DISABLE. When it is ready to be activated, you may enable it using ALTER EVENT. Another option is DISABLE ON SLAVE, which indicates that an event was created on a master and has been replicated to the slave, which is prevented from executing the event. If DISABLE ON SLAVE is specifically set, the event will not be executed.

COMMENT

The COMMENT clause may be used to set a comment for the event. Maximum length for comments is 64 characters. The comment is a string, so it must be quoted. To see events comments, you can query the INFORMATION_SCHEMA.EVENTS table (the column is named EVENT_COMMENT).

Examples

Minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

An event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

Next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

OR REPLACE and IF NOT EXISTS:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
ERROR 1537 (HY000): Event 'myevent' already exists

CREATE OR REPLACE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;;
Query OK, 0 rows affected (0.00 sec)

CREATE EVENT IF NOT EXISTS myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

 SHOW WARNINGS;
+-------+------+--------------------------------+
| Level | Code | Message                        |
+-------+------+--------------------------------+
| Note  | 1537 | Event 'myevent' already exists |
+-------+------+--------------------------------+

See Also

CREATE INDEX

Syntax

CREATE [OR REPLACE] [UNIQUE|FULLTEXT|SPATIAL] INDEX 
  [IF NOT EXISTS] index_name
    [index_type]
    ON tbl_name (index_col_name,...)
    [WAIT n | NOWAIT]
    [index_option]
    [algorithm_option | lock_option] ...

index_col_name:
    col_name [(length)] [ASC | DESC]

index_type:
    USING {BTREE | HASH | RTREE}

index_option:
    [ KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES| NO} ]
  [ IGNORED | NOT IGNORED ]

algorithm_option:
    ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}

lock_option:
    LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}

Description

CREATE INDEX is mapped to an ALTER TABLE statement to create indexes. See ALTER TABLE. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

Another shortcut, DROP INDEX, allows the removal of an index.

For valid identifiers to use as index names, see Identifier Names.

Note that KEY_BLOCK_SIZE is currently ignored in CREATE INDEX, although it is included in the output of SHOW CREATE TABLE.

Privileges

Executing the CREATE INDEX statement requires the INDEX privilege for the table or the database.

Online DDL

Online DDL is supported with the ALGORITHM and LOCK clauses.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

CREATE OR REPLACE INDEX

MariaDB starting with 10.1.4

The OR REPLACE clause was added in MariaDB 10.1.4.

If the OR REPLACE clause is used and if the index already exists, then instead of returning an error, the server will drop the existing index and replace it with the newly defined index.

CREATE INDEX IF NOT EXISTS

If the IF NOT EXISTS clause is used, then the index will only be created if an index with the same name does not already exist. If the index already exists, then a warning will be triggered by default.

Index Definitions

See CREATE TABLE: Index Definitions for information about index definitions.

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

ALGORITHM

See ALTER TABLE: ALGORITHM for more information.

LOCK

See ALTER TABLE: LOCK for more information.

Progress Reporting

MariaDB provides progress reporting for CREATE INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

CREATE INDEX ON tab (num);;
Stage: 1 of 2 'copy to tmp table'    46% of stage

The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table.

See Progress Reporting for more information.

WITHOUT OVERLAPS

MariaDB starting with 10.5.3

The WITHOUT OVERLAPS clause allows one to constrain a primary or unique index such that application-time periods cannot overlap.

Examples

Creating a unique index:

CREATE UNIQUE INDEX HomePhone ON Employees(Home_Phone);

OR REPLACE and IF NOT EXISTS:

CREATE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX xi ON xx5 (x);
ERROR 1061 (42000): Duplicate key name 'xi'

CREATE OR REPLACE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX IF NOT EXISTS xi ON xx5 (x);
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message                 |
+-------+------+-------------------------+
| Note  | 1061 | Duplicate key name 'xi' |
+-------+------+-------------------------+

From MariaDB 10.5.3, creating a unique index for an application-time period table with a WITHOUT OVERLAPS constraint:

CREATE UNIQUE INDEX u ON rooms (room_number, p WITHOUT OVERLAPS);

See Also

CREATE PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

CREATE
    [ OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PACKAGE [ IF NOT EXISTS ]
    [ db_name . ] package_name
    [ package_characteristic ... ]
{ AS | IS }
    [ package_specification_element ... ]
END [ package_name ]


package_characteristic:
    COMMENT 'string'
  | SQL SECURITY { DEFINER | INVOKER }


package_specification_element:
    FUNCTION_SYM package_specification_function ;
  | PROCEDURE_SYM package_specification_procedure ;


package_specification_function:
    func_name [ ( func_param [, func_param]... ) ]
    RETURNS func_return_type
    [ package_routine_characteristic... ]

package_specification_procedure:
    proc_name [ ( proc_param [, proc_param]... ) ]
    [ package_routine_characteristic... ]

func_return_type:
    type

func_param:
    param_name [ IN | OUT | INOUT | IN OUT ] type

proc_param:
    param_name [ IN | OUT | INOUT | IN OUT ] type

type:
    Any valid MariaDB explicit or anchored data type


package_routine_characteristic:
      COMMENT  'string'
    | LANGUAGE SQL
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }

Description

The CREATE PACKAGE statement can be used when Oracle SQL_MODE is set.

The CREATE PACKAGE creates the specification for a stored package (a collection of logically related stored objects). A stored package specification declares public routines (procedures and functions) of the package, but does not implement these routines.

A package whose specification was created by the CREATE PACKAGE statement, should later be implemented using the CREATE PACKAGE BODY statement.

Function parameter quantifiers IN | OUT | INOUT | IN OUT

MariaDB starting with 10.8.0

The function parameter quantifiers for IN, OUT, INOUT, and IN OUT where added in a 10.8.0 preview release. Prior to 10.8.0 quantifiers were supported only in procedures.

OUT, INOUT and its equivalent IN OUT, are only valid if called from SET and not SELECT. These quantifiers are especially useful for creating functions and procedures with more than one return value. This allows functions and procedures to be more complex and nested.

Examples

SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
DELIMITER ;

See Also

CREATE PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

CREATE [ OR REPLACE ]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PACKAGE BODY
    [ IF NOT EXISTS ]
    [ db_name . ] package_name
    [ package_characteristic... ]
{ AS | IS }
    package_implementation_declare_section
    package_implementation_executable_section
END [ package_name]


package_implementation_declare_section:
    package_implementation_item_declaration
      [ package_implementation_item_declaration... ]
      [ package_implementation_routine_definition... ]
  | package_implementation_routine_definition
      [ package_implementation_routine_definition...]

package_implementation_item_declaration:
    variable_declaration ;

variable_declaration:
    variable_name[,...] type [:= expr ]

package_implementation_routine_definition:
    FUNCTION package_specification_function
       [ package_implementation_function_body ] ;
  | PROCEDURE package_specification_procedure
       [ package_implementation_procedure_body ] ;


package_implementation_function_body:
    { AS | IS } package_routine_body [func_name]

package_implementation_procedure_body:
    { AS | IS } package_routine_body [proc_name]

package_routine_body:
    [ package_routine_declarations ]
    BEGIN
      statements [ EXCEPTION exception_handlers ]
    END


package_routine_declarations:
    package_routine_declaration ';' [package_routine_declaration ';']...


package_routine_declaration:
          variable_declaration
        | condition_name CONDITION FOR condition_value
        | user_exception_name EXCEPTION
        | CURSOR_SYM cursor_name
          [ ( cursor_formal_parameters ) ]
          IS select_statement
        ;


package_implementation_executable_section:
          END
        | BEGIN
            statement ; [statement ; ]...
          [EXCEPTION exception_handlers]
          END

exception_handlers:
           exception_handler [exception_handler...]

exception_handler:
          WHEN_SYM condition_value [, condition_value]...
            THEN_SYM statement ; [statement ;]...

condition_value:
          condition_name
        | user_exception_name
        | SQLWARNING
        | SQLEXCEPTION
        | NOT FOUND
        | OTHERS_SYM
        | SQLSTATE [VALUE] sqlstate_value
        | mariadb_error_code

Description

The CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

The CREATE PACKAGE BODY statement creates the package body for a stored package. The package specification must be previously created using the CREATE PACKAGE statement.

A package body provides implementations of the package public routines and can optionally have:

  • package-wide private variables
  • package private routines
  • forward declarations for private routines
  • an executable initialization section

Examples

SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
CREATE PACKAGE BODY employee_tools AS
  -- package body variables
  stdRaiseAmount DECIMAL(10,2):=500;

  -- private routines
  PROCEDURE log (eid INT, ecmnt TEXT) AS
  BEGIN
    INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
  END;

  -- public routines
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
    eid INT;
  BEGIN
    INSERT INTO employee (name, salary) VALUES (ename, esalary);
    eid:= last_insert_id();
    log(eid, 'hire ' || ename);
  END;

  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
    nSalary DECIMAL(10,2);
  BEGIN
    SELECT salary INTO nSalary FROM employee WHERE id=eid;
    log(eid, 'getSalary id=' || eid || ' salary=' || nSalary);
    RETURN nSalary;
  END;

  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
  BEGIN
    UPDATE employee SET salary=salary+amount WHERE id=eid;
    log(eid, 'raiseSalary id=' || eid || ' amount=' || amount);
  END;

  PROCEDURE raiseSalaryStd(eid INT) AS
  BEGIN
    raiseSalary(eid, stdRaiseAmount);
    log(eid, 'raiseSalaryStd id=' || eid);
  END;

BEGIN
  -- This code is executed when the current session
  -- accesses any of the package routines for the first time
  log(0, 'Session ' || connection_id() || ' ' || current_user || ' started');
END;
$$

DELIMITER ;

See Also

DROP DATABASE

Syntax

DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

Description

DROP DATABASE drops all tables in the database and deletes the database. Be very careful with this statement! To use DROP DATABASE, you need the DROP privilege on the database. DROP SCHEMA is a synonym for DROP DATABASE.

Important: When a database is dropped, user privileges on the database are not automatically dropped. See GRANT.

IF EXISTS

Use IF EXISTS to prevent an error from occurring for databases that do not exist. A NOTE is generated for each non-existent database when using IF EXISTS. See SHOW WARNINGS.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL.

DROP DATABASE is implemented as

loop over all tables
  DROP TABLE table

Each individual DROP TABLE is atomic while DROP DATABASE as a whole is crash-safe.

Examples

DROP DATABASE bufg;
Query OK, 0 rows affected (0.39 sec)

DROP DATABASE bufg;
ERROR 1008 (HY000): Can't drop database 'bufg'; database doesn't exist

 \W
Show warnings enabled.

DROP DATABASE IF EXISTS bufg;
Query OK, 0 rows affected, 1 warning (0.00 sec)
Note (Code 1008): Can't drop database 'bufg'; database doesn't exist

See Also

CREATE SEQUENCE

MariaDB starting with 10.3

CREATE SEQUENCE was introduced in MariaDB 10.3.

Syntax

CREATE [OR REPLACE] [TEMPORARY] SEQUENCE [IF NOT EXISTS] sequence_name [ INCREMENT [ BY | = ] increment ] [ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ] [ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ] [ START [ WITH | = ] start ] [ CACHE [=] cache | NOCACHE ] [ CYCLE | NOCYCLE] [table_options]

The options for CREATE SEQUENCE can be given in any order, optionally followed by table_options.

table_options can be any of the normal table options in CREATE TABLE but the most usable ones are ENGINE=... and COMMENT=.

NOMAXVALUE and NOMINVALUE are there to allow one to create SEQUENCEs using the Oracle syntax.

Description

CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to CACHE) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID().

CREATE SEQUENCE requires the CREATE privilege.

DROP SEQUENCE can be used to drop a sequence, and ALTER SEQUENCE to change it.

Arguments to Create

The following options may be used:

OptionDefault value Description
INCREMENT 1Increment to use for values. May be negative. Setting an increment of 0 causes the sequence to use the value of the auto_increment_increment system variable at the time of creation, which is always a positive number. (see MDEV-16035).
MINVALUE1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0Minimum value for the sequence
MAXVALUE9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0Max value for sequence
STARTMINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0First value that the sequence will generate
CACHE1000 Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out.

If CYCLE is used then the sequence should start again from MINVALUE after it has run out of values. Default value is NOCYCLE.

Constraints on Create Arguments

To be able to create a legal sequence, the following must hold:

  • MAXVALUE >= start
  • MAXVALUE > MINVALUE
  • START >= MINVALUE
  • MAXVALUE <= 9223372036854775806 (LONGLONG_MAX-1)
  • MINVALUE >= -9223372036854775807 (LONGLONG_MIN+1)

Note that sequences can't generate the maximum/minimum 64 bit number because of the constraint of MINVALUE and MAXVALUE.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE SEQUENCE is atomic.

Examples

CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;

CREATE SEQUENCE s2 START WITH -100 INCREMENT BY -10;

The following statement fails, as the increment conflicts with the defaults

CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10;
ERROR 4082 (HY000): Sequence 'test.s3' values are conflicting

The sequence can be created by specifying workable minimum and maximum values:

CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10 MINVALUE=-100 MAXVALUE=1000;

See Also

DROP EVENT

Syntax

DROP EVENT [IF EXISTS] event_name

Description

This statement drops the event named event_name. The event immediately ceases being active, and is deleted completely from the server.

If the event does not exist, the error ERROR 1517 (HY000): Unknown event 'event_name' results. You can override this and cause the statement to generate a NOTE for non-existent events instead by using IF EXISTS. See SHOW WARNINGS.

This statement requires the EVENT privilege. In MySQL 5.1.11 and earlier, an event could be dropped only by its definer, or by a user having the SUPER privilege.

Examples

DROP EVENT myevent3;

Using the IF EXISTS clause:

DROP EVENT IF EXISTS myevent3;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message                       |
+-------+------+-------------------------------+
| Note  | 1305 | Event myevent3 does not exist |
+-------+------+-------------------------------+

See also

DROP FUNCTION

Syntax

DROP FUNCTION [IF EXISTS] f_name

Description

The DROP FUNCTION statement is used to drop a stored function or a user-defined function (UDF). That is, the specified routine is removed from the server, along with all privileges specific to the function. You must have the ALTER ROUTINE privilege for the routine in order to drop it. If the automatic_sp_privileges server system variable is set, both the ALTER ROUTINE and EXECUTE privileges are granted automatically to the routine creator - see Stored Routine Privileges.

IF EXISTS

The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS.

For dropping a user-defined functions (UDF), see DROP FUNCTION UDF.

Examples

DROP FUNCTION hello;
Query OK, 0 rows affected (0.042 sec)

DROP FUNCTION hello;
ERROR 1305 (42000): FUNCTION test.hello does not exist

DROP FUNCTION IF EXISTS hello;
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message                            |
+-------+------+------------------------------------+
| Note  | 1305 | FUNCTION test.hello does not exist |
+-------+------+------------------------------------+

See Also

CREATE SERVER

Syntax

CREATE [OR REPLACE] SERVER [IF NOT EXISTS] server_name
    FOREIGN DATA WRAPPER wrapper_name
    OPTIONS (option [, option] ...)

option:
  { HOST character-literal
  | DATABASE character-literal
  | USER character-literal
  | PASSWORD character-literal
  | SOCKET character-literal
  | OWNER character-literal
  | PORT numeric-literal }

Description

This statement creates the definition of a server for use with the Spider, Connect, FEDERATED or FederatedX storage engine. The CREATE SERVER statement creates a new row within the servers table within the mysql database. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

The server_name should be a unique reference to the server. Server definitions are global within the scope of the server, it is not possible to qualify the server definition to a specific database. server_name has a maximum length of 64 characters (names longer than 64 characters are silently truncated), and is case insensitive. You may specify the name as a quoted string.

The wrapper_name may be quoted with single quotes. Supported values are:

For each option you must specify either a character literal or numeric literal. Character literals are UTF-8, support a maximum length of 64 characters and default to a blank (empty) string. String literals are silently truncated to 64 characters. Numeric literals must be a number between 0 and 9999, default value is 0.

Note: The OWNER option is currently not applied, and has no effect on the ownership or operation of the server connection that is created.

The CREATE SERVER statement creates an entry in the mysql.servers table that can later be used with the CREATE TABLE statement when creating a Spider, Connect, FederatedX or FEDERATED table. The options that you specify will be used to populate the columns in the mysql.servers table. The table columns are Server_name, Host, Db, Username, Password, Port and Socket.

DROP SERVER removes a previously created server definition.

CREATE SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

For valid identifiers to use as server names, see Identifier Names.

OR REPLACE

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP SERVER IF EXISTS name;
CREATE SERVER server_name ...;

IF NOT EXISTS

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the server already exists. Cannot be used together with OR REPLACE.

Examples

CREATE SERVER s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');

OR REPLACE and IF NOT EXISTS:

CREATE SERVER s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
ERROR 1476 (HY000): The foreign server, s, you are trying to create already exists

CREATE OR REPLACE SERVER s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
Query OK, 0 rows affected (0.00 sec)

CREATE SERVER IF NOT EXISTS s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------------------------+
| Level | Code | Message                                                        |
+-------+------+----------------------------------------------------------------+
| Note  | 1476 | The foreign server, s, you are trying to create already exists |
+-------+------+----------------------------------------------------------------+

See Also

DROP INDEX

Syntax

DROP INDEX [IF EXISTS] index_name ON tbl_name 
    [WAIT n |NOWAIT]

Description

DROP INDEX drops the index named index_name from the table tbl_name. This statement is mapped to an ALTER TABLE statement to drop the index.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

See ALTER TABLE.

Another shortcut, CREATE INDEX, allows the creation of an index.

To remove the primary key, `PRIMARY` must be specified as index_name. Note that the quotes are necessary, because PRIMARY is a keyword.

Privileges

Executing the DROP INDEX statement requires the INDEX privilege for the table or the database.

Online DDL

Online DDL is used by default with InnoDB, when the drop index operation supports it.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

DROP INDEX IF EXISTS ...

If the IF EXISTS clause is used, then MariaDB will return a warning instead of an error if the index does not exist.

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

Progress Reporting

MariaDB provides progress reporting for DROP INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

See Also

CREATE TRIGGER

Syntax

CREATE [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    TRIGGER [IF NOT EXISTS] trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW
   [{ FOLLOWS | PRECEDES } other_trigger_name ]
   trigger_stmt;

Description

This statement creates a new trigger. A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. The trigger becomes associated with the table named tbl_name, which must refer to a permanent table. You cannot associate a trigger with a TEMPORARY table or a view.

CREATE TRIGGER requires the TRIGGER privilege for the table associated with the trigger.

MariaDB starting with 10.2.3

You can have multiple triggers for the same trigger_time and trigger_event.

For valid identifiers to use as trigger names, see Identifier Names.

OR REPLACE

MariaDB starting with 10.1.4

If used and the trigger already exists, instead of an error being returned, the existing trigger will be dropped and replaced by the newly defined trigger.

DEFINER

The DEFINER clause determines the security context to be used when checking access privileges at trigger activation time. Usage requires the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege.

IF NOT EXISTS

MariaDB starting with 10.1.4

If the IF NOT EXISTS clause is used, the trigger will only be created if a trigger of the same name does not exist. If the trigger already exists, by default a warning will be returned.

trigger_time

trigger_time is the trigger action time. It can be BEFORE or AFTER to indicate that the trigger activates before or after each row to be modified.

trigger_event

trigger_event indicates the kind of statement that activates the trigger. The trigger_event can be one of the following:

  • INSERT: The trigger is activated whenever a new row is inserted into the table; for example, through INSERT, LOAD DATA, and REPLACE statements.
  • UPDATE: The trigger is activated whenever a row is modified; for example, through UPDATE statements.
  • DELETE: The trigger is activated whenever a row is deleted from the table; for example, through DELETE and REPLACE statements. However, DROP TABLE and TRUNCATE statements on the table do not activate this trigger, because they do not use DELETE. Dropping a partition does not activate DELETE triggers, either.

FOLLOWS/PRECEDES other_trigger_name

MariaDB starting with 10.2.3

The FOLLOWS other_trigger_name and PRECEDES other_trigger_name options were added in MariaDB 10.2.3 as part of supporting multiple triggers per action time. This is the same syntax used by MySQL 5.7, although MySQL 5.7 does not have multi-trigger support.

FOLLOWS adds the new trigger after another trigger while PRECEDES adds the new trigger before another trigger. If neither option is used, the new trigger is added last for the given action and time.

FOLLOWS and PRECEDES are not stored in the trigger definition. However the trigger order is guaranteed to not change over time. mariadb-dump/mysqldump and other backup methods will not change trigger order. You can verify the trigger order from the ACTION_ORDER column in INFORMATION_SCHEMA.TRIGGERS table.

SELECT trigger_name, action_order FROM information_schema.triggers 
  WHERE event_object_table='t1';

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE TRIGGER is atomic.

Examples

CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals FOR EACH ROW 
   UPDATE animal_count SET animal_count.animals = animal_count.animals+1;

OR REPLACE and IF NOT EXISTS

CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
ERROR 1359 (HY000): Trigger already exists

CREATE OR REPLACE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals  FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
Query OK, 0 rows affected (0.12 sec)

CREATE DEFINER=`root`@`localhost` TRIGGER IF NOT EXISTS increment_animal
  AFTER INSERT ON animals FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1359 | Trigger already exists |
+-------+------+------------------------+
1 row in set (0.00 sec)

See Also

DROP PROCEDURE

Syntax

DROP PROCEDURE [IF EXISTS] sp_name

Description

This statement is used to drop a stored procedure. That is, the specified routine is removed from the server along with all privileges specific to the procedure. You must have the ALTER ROUTINE privilege for the routine. If the automatic_sp_privileges server system variable is set, that privilege and EXECUTE are granted automatically to the routine creator - see Stored Routine Privileges.

The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the procedure or function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS.

While this statement takes effect immediately, threads which are executing a procedure can continue execution.

Examples

DROP PROCEDURE simpleproc;

IF EXISTS:

DROP PROCEDURE simpleproc;
ERROR 1305 (42000): PROCEDURE test.simpleproc does not exist

DROP PROCEDURE IF EXISTS simpleproc;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------+
| Level | Code | Message                                  |
+-------+------+------------------------------------------+
| Note  | 1305 | PROCEDURE test.simpleproc does not exist |
+-------+------+------------------------------------------+

See Also

DROP SEQUENCE

MariaDB starting with 10.3

DROP SEQUENCE was introduced in MariaDB 10.3.

Syntax

DROP [TEMPORARY] SEQUENCE [IF EXISTS] [/*COMMENT TO SAVE*/] sequence_name [, sequence_name] ...

Description

DROP SEQUENCE removes one or more sequences created with CREATE SEQUENCE. You must have the DROP privilege for each sequence. MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist.

Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT.

If another connection is using the sequence, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

For each referenced sequence, DROP SEQUENCE drops a temporary sequence with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary sequence with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary sequence will not accidentally be dropped.

Use IF EXISTS to prevent an error from occurring for sequences that do not exist. A NOTE is generated for each non-existent sequence when using IF EXISTS. See SHOW WARNINGS.

DROP SEQUENCE requires the DROP privilege.

Notes

DROP SEQUENCE only removes sequences, not tables. However, DROP TABLE can remove both sequences and tables.

See Also

DROP SERVER

Syntax

DROP SERVER [ IF EXISTS ] server_name

Description

Drops the server definition for the server named server_name. The corresponding row within the mysql.servers table will be deleted. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

Dropping a server for a table does not affect any FederatedX, FEDERATED, Connect or Spider tables that used this connection information when they were created.

DROP SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will not return an error if the server does not exist. Unlike all other statements, DROP SERVER IF EXISTS does not issue a note if the server does not exist. See MDEV-9400.

Examples

DROP SERVER s;

IF EXISTS:

DROP SERVER s;
ERROR 1477 (HY000): The foreign server name you are trying to reference 
  does not exist. Data source error:  s

DROP SERVER IF EXISTS s;
Query OK, 0 rows affected (0.00 sec)

See Also

DROP TRIGGER

Syntax

DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name

Description

This statement drops a trigger. The schema (database) name is optional. If the schema is omitted, the trigger is dropped from the default schema. Its use requires the TRIGGER privilege for the table associated with the trigger.

Use IF EXISTS to prevent an error from occurring for a trigger that does not exist. A NOTE is generated for a non-existent trigger when using IF EXISTS. See SHOW WARNINGS.

Note: Triggers for a table are also dropped if you drop the table.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and DROP TRIGGER is atomic.

Examples

DROP TRIGGER test.example_trigger;

Using the IF EXISTS clause:

DROP TRIGGER IF EXISTS test.example_trigger;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1360 | Trigger does not exist |
+-------+------+------------------------+

See Also

DROP VIEW

Syntax

DROP VIEW [IF EXISTS]
    view_name [, view_name] ...
    [RESTRICT | CASCADE]

Description

DROP VIEW removes one or more views. You must have the DROP privilege for each view. If any of the views named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing views it was unable to drop, but it also drops all of the views in the list that do exist.

The IF EXISTS clause prevents an error from occurring for views that don't exist. When this clause is given, a NOTE is generated for each non-existent view. See SHOW WARNINGS.

RESTRICT and CASCADE, if given, are parsed and ignored.

It is possible to specify view names as db_name.view_name. This is useful to delete views from multiple databases with one statement. See Identifier Qualifiers for details.

The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session.

If a view references another view, it will be possible to drop the referenced view. However, the other view will reference a view which does not exist any more. Thus, querying it will produce an error similar to the following:

ERROR 1356 (HY000): View 'db_name.view_name' references invalid table(s) or 
column(s) or function(s) or definer/invoker of view lack rights to use them

This problem is reported in the output of CHECK TABLE.

Note that it is not necessary to use DROP VIEW to replace an existing view, because CREATE VIEW has an OR REPLACE clause.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and DROP VIEW for a singular view is atomic. Dropping multiple views is crash-safe.

Examples

DROP VIEW v,v2;

Given views v and v2, but no view v3

DROP VIEW v,v2,v3;
ERROR 1051 (42S02): Unknown table 'v3'
DROP VIEW IF EXISTS v,v2,v3;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message                 |
+-------+------+-------------------------+
| Note  | 1051 | Unknown table 'test.v3' |
+-------+------+-------------------------+

See Also

MERGE

Description

The MERGE storage engine, also known as the MRG_MyISAM engine, is a collection of identical MyISAM tables that can be used as one. "Identical" means that all tables have identical column and index information. You cannot merge MyISAM tables in which the columns are listed in a different order, do not have exactly the same columns, or have the indexes in different order. However, any or all of the MyISAM tables can be compressed with myisampack. Columns names and indexes names can be different, as long as data types and NULL/NOT NULL clauses are the same. Differences in table options such as AVG_ROW_LENGTH, MAX_ROWS, or PACK_KEYS do not matter.

Each index in a MERGE table must match an index in underlying MyISAM tables, but the opposite is not true. Also, a MERGE table cannot have a PRIMARY KEY or UNIQUE indexes, because it cannot enforce uniqueness over all underlying tables.

The following options are meaningful for MERGE tables:

  • UNION. This option specifies the list of the underlying MyISAM tables. The list is enclosed between parentheses and separated with commas.
  • INSERT_METHOD. This options specifies whether, and how, INSERTs are allowed for the table. Allowed values are: NO (INSERTs are not allowed), FIRST (new rows will be written into the first table specified in the UNION list), LAST (new rows will be written into the last table specified in the UNION list). The default value is NO.

If you define a MERGE table with a definition which is different from the underlying MyISAM tables, or one of the underlying tables is not MyISAM, the CREATE TABLE statement will not return any error. But any statement which involves the table will produce an error like the following:

ERROR 1168 (HY000): Unable to open underlying table which is differently defined 
  or of non-MyISAM type or doesn't exist

A CHECK TABLE will show more information about the problem.

The error is also produced if the table is properly define, but an underlying table's definition changes at some point in time.

If you try to insert a new row into a MERGE table with INSERT_METHOD=NO, you will get an error like the following:

ERROR 1036 (HY000): Table 'tbl_name' is read only

It is possible to build a MERGE table on MyISAM tables which have one or more virtual columns. MERGE itself does not support virtual columns, thus such columns will be seen as regular columns. The data types and sizes will still need to be identical, and they cannot be NOT NULL.

Examples

CREATE TABLE t1 (
    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    message CHAR(20)) ENGINE=MyISAM;

CREATE TABLE t2 (
    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    message CHAR(20)) ENGINE=MyISAM;


INSERT INTO t1 (message) VALUES ('Testing'),('table'),('t1');

INSERT INTO t2 (message) VALUES ('Testing'),('table'),('t2');

CREATE TABLE total (
    a INT NOT NULL AUTO_INCREMENT,
    message CHAR(20), INDEX(a))
    ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST;

SELECT * FROM total;
+---+---------+
| a | message |
+---+---------+
| 1 | Testing |
| 2 | table   |
| 3 | t1      |
| 1 | Testing |
| 2 | table   |
| 3 | t2      |
+---+---------+

In the following example, we'll create three MyISAM tables, and then a MERGE table on them. However, one of them uses a different data type for the column b, so a SELECT will produce an error:

CREATE TABLE t1 (
  a INT,
  b INT
) ENGINE = MyISAM;

CREATE TABLE t2 (
  a INT,
  b INT
) ENGINE = MyISAM;

CREATE TABLE t3 (
  a INT,
  b TINYINT
) ENGINE = MyISAM;

CREATE TABLE t_mrg (
  a INT,
  b INT
) ENGINE = MERGE,UNION=(t1,t2,t3);

SELECT * FROM t_mrg;
ERROR 1168 (HY000): Unable to open underlying table which is differently defined
 or of non-MyISAM type or doesn't exist

To find out what's wrong, we'll use a CHECK TABLE:

CHECK TABLE t_mrg;
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| Table      | Op    | Msg_type | Msg_text                                                      |
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| test.t_mrg | check | Error    | Table 'test.t3' is differently defined or of non-MyISAM type or doesn't exist                       |
| test.t_mrg | check | Error    | Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist |
| test.t_mrg | check | error    | Corrupt                                                      |
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+

Now, we know that the problem is in t3's definition.

NEXT VALUE for sequence_name

MariaDB starting with 10.3

SEQUENCEs were introduced in MariaDB 10.3

Syntax

NEXT VALUE FOR sequence

or

NEXTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.nextval

NEXT VALUE FOR is ANSI SQL syntax while NEXTVAL() is PostgreSQL syntax.

Description

Generate next value for a SEQUENCE.

  • You can greatly speed up NEXT VALUE by creating the sequence with the CACHE option. If not, every NEXT VALUE usage will cause changes in the stored SEQUENCE table.
  • When using NEXT VALUE the value will be reserved at once and will not be reused, except if the SEQUENCE was created with CYCLE. This means that when you are using SEQUENCEs you have to expect gaps in the generated sequence numbers.
  • If one updates the SEQUENCE with SETVAL() or ALTER SEQUENCE ... RESTART, NEXT VALUE FOR will notice this and start from the next requested value.
  • FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the SEQUENCE object. In effect, this will discard the cached values.
  • A server restart (or closing the current connection) also causes a drop of all cached values. The cached sequence numbers are reserved only for the current connection.
  • NEXT VALUE requires the INSERT privilege.
MariaDB starting with 10.3.3
  • You can also use NEXT VALUE FOR sequence for column DEFAULT.

See Also

PREVIOUS VALUE FOR sequence_name

MariaDB starting with 10.3

SEQUENCEs were introduced in MariaDB 10.3.

Syntax

PREVIOUS VALUE FOR sequence_name

or

LASTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.currval

PREVIOUS VALUE FOR is IBM DB2 syntax while LASTVAL() is PostgreSQL syntax.

Description

Get last value in the current connection generated from a sequence.

  • If the sequence has not yet been used by the connection, PREVIOUS VALUE FOR returns NULL (the same thing applies with a new connection which doesn't see a last value for an existing sequence).
  • If a SEQUENCE has been dropped and re-created then it's treated as a new SEQUENCE and PREVIOUS VALUE FOR will return NULL.
  • FLUSH TABLES has no effect on PREVIOUS VALUE FOR.
  • Previous values for all used sequences are stored per connection until connection ends.
  • PREVIOUS VALUE FOR requires the SELECT privilege.

Example

MariaDB [test]> CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;
Query OK, 0 rows affected (0.026 sec)

MariaDB [test]> SELECT PREVIOUS VALUE FOR s;
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                 NULL |
+----------------------+
1 row in set (0.000 sec)

# The function works for sequences only, if the table is used an error is generated
MariaDB [test]> SELECT PREVIOUS VALUE FOR t;
ERROR 4089 (42S02): 'test.t' is not a SEQUENCE

# Call the NEXT VALUE FOR s:
MariaDB [test]> SELECT NEXT VALUE FOR s;
+------------------+
| NEXT VALUE FOR s |
+------------------+
|              100 |
+------------------+
1 row in set (0.000 sec)

MariaDB [test]> SELECT PREVIOUS VALUE FOR s;
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                  100 |
+----------------------+
1 row in set (0.000 sec)

Now try to start the new connection and check that the last value is still NULL, before updating the value in the new connection after the output of the new connection gets current value (110 in the example below). Note that first connection cannot see this change and the result of last value still remains the same (100 in the example above).

$ .mysql -uroot test -e"SELECT PREVIOUS VALUE FOR s; SELECT NEXT VALUE FOR s; SELECT PREVIOUS VALUE FOR s;"
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                 NULL |
+----------------------+
+------------------+
| NEXT VALUE FOR s |
+------------------+
|              110 |
+------------------+
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                  110 |
+----------------------+

See Also

Sequence Overview

MariaDB starting with 10.3

Sequences were introduced in MariaDB 10.3.

Introduction

A sequence is an object that generates a sequence of numeric values, as specified by the CREATE SEQUENCE statement.

CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to the CACHE value in the CREATE SEQUENCE statement, by default 1000) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID().

Creating a Sequence

The CREATE SEQUENCE statement is used to create a sequence. Here is an example of a sequence starting at 100, incrementing by 10 each time:

CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;

The CREATE SEQUENCE statement, along with defaults, can be viewd with the SHOW CREATE SEQUENCE STATEMENT, for example:

SHOW CREATE SEQUENCE s\G
*************************** 1. row ***************************
       Table: s
Create Table: CREATE SEQUENCE `s` start with 100 minvalue 1 maxvalue 9223372036854775806 
  increment by 10 cache 1000 nocycle ENGINE=InnoDB

Using Sequence Objects

To get the next value from a sequence, use

NEXT VALUE FOR sequence_name

or

NEXTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.nextval

For retrieving the last value used by the current connection from a sequence use:

PREVIOUS VALUE FOR sequence_name

or

LASTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.currval

For example:

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        100 |
+------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        110 |
+------------+

SELECT LASTVAL(s);
+------------+
| LASTVAL(s) |
+------------+
|        110 |
+------------+

Using Sequences in DEFAULT

MariaDB starting with 10.3.3

Starting from 10.3.3 you can use Sequences in DEFAULT:

create sequence s1;
create table t1 (a int primary key default (next value for s1), b int);
insert into t1 (b) values (1),(2);
select * from t1;
+---+------+
| a | b    |
+---+------+
| 1 |    1 |
| 2 |    2 |
+---+------+

Changing a Sequence

The ALTER SEQUENCE statement is used for changing sequences. For example, to restart the sequence at another value:

ALTER SEQUENCE s RESTART 50;

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|         50 |
+------------+

The SETVAL function can also be used to set the next value to be returned for a SEQUENCE, for example:

SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
|            100 |
+----------------+

SETVAL can only be used to increase the sequence value. Attempting to set a lower value will fail, returning NULL:

SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
|          NULL |
+---------------+

Dropping a Sequence

The DROP SEQUENCE statement is used to drop a sequence, for example:

DROP SEQUENCE s;

Replication

If one wants to use Sequences in a master-master setup or with Galera one should use INCREMENT=0. This will tell the Sequence to use auto_increment_increment and auto_increment_offset to generate unique values for each server.

Standards Compliance

MariaDB 10.3 supports both ANSI SQL and Oracle syntax for sequences.

However as SEQUENCE is implemented as a special kind of table, it uses the same namespace as tables. The benefits are that sequences show up in SHOW TABLES, and one can also create a sequence with CREATE TABLE and drop it with DROP TABLE. One can SELECT from it as from any other table. This ensures that all old tools that work with tables should work with sequences.

Since sequence objects act as regular tables in many contexts, they will be affected by LOCK TABLES. This is not the case in other DBMS, such as Oracle, where LOCK TABLE does not affect sequences.

Notes

One of the goals with the Sequence implementation is that all old tools, such as mysqldump, should work unchanged, while still keeping the normal usage of sequence standard compatibly.

To make this possible, sequence is currently implemented as a table with a few exclusive properties.

The special properties for sequence tables are:

  • A sequence table has always one row.
  • When one creates a sequence, either with CREATE TABLE or CREATE SEQUENCE, one row will be inserted.
  • If one tries to insert into a sequence table, the single row will be updated. This allows mysqldump to work but also gives the additional benefit that one can change all properties of a sequence with a single insert. New applications should of course also use ALTER SEQUENCE.
  • UPDATE or DELETE can't be performed on Sequence objects.
  • Doing a select on the sequence shows the current state of the sequence, except the values that are reserved in the cache. The next_value column shows the next value not reserved by the cache.
  • FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the Sequence object. In effect, this will discard the cached values.
  • A number of normal table operations work on Sequence tables. See next section.

Table Operations that Work with Sequences

Implementation

Internally, sequence tables are created as a normal table without rollback (the InnoDB, Aria and MySAM engines support this), wrapped by a sequence engine object. This allowed us to create sequences with almost no performance impact for normal tables. (The cost is one 'if' per insert if the binary log is enabled).

Underlying Table Structure

The following example shows the table structure of sequences and how it can be used as a table. (Output of results are slightly edited to make them easier to read)

create sequence t1; show create sequence t1\G ***** 1. row ***** CREATE SEQUENCE `t1` start with 1 minvalue 1 maxvalue 9223372036854775806 increment by 1 cache 1000 nocycle ENGINE=InnoDB

show create table t1\G ***** 1. row ***** Create Table: CREATE TABLE `t1` ( `next_not_cached_value` bigint(21) NOT NULL, `minimum_value` bigint(21) NOT NULL, `maximum_value` bigint(21) NOT NULL, `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used', `increment` bigint(21) NOT NULL COMMENT 'increment value', `cache_size` bigint(21) unsigned NOT NULL, `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed', `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done' ) ENGINE=InnoDB SEQUENCE=1

select * from t1\G next_not_cached_value: 1 minimum_value: 1 maximum_value: 9223372036854775806 start_value: 1 increment: 1 cache_size: 1000 cycle_option: 0 cycle_count: 0

The cycle_count column is incremented every time the sequence wraps around.

Credits

  • Thanks to Jianwe Zhao from Aliyun for his work on SEQUENCE in AliSQL, which gave ideas and inspiration for this work.
  • Thanks to Peter Gulutzan,who helped test and gave useful comments about the implementation.

See Also

SETVAL()

MariaDB starting with 10.3.1

SEQUENCEs were introduced in MariaDB 10.3.

Syntax

SETVAL(sequence_name, next_value, [is_used, [round]])

Description

Set the next value to be returned for a SEQUENCE.

This function is compatible with PostgreSQL syntax, extended with the round argument.

If the is_used argument is not given or is 1 or true, then the next used value will one after the given value. If is_used is 0 or false then the next generated value will be the given value.

If round is used then it will set the round value (or the internal cycle count, starting at zero) for the sequence. If round is not used, it's assumed to be 0.

next_value must be an integer literal.

For SEQUENCE tables defined with CYCLE (see CREATE SEQUENCE) one should use both next_value and round to define the next value. In this case the current sequence value is defined to be round, next_value.

The result returned by SETVAL() is next_value or NULL if the given next_value and round is smaller than the current value.

SETVAL() will not set the SEQUENCE value to a something that is less than its current value. This is needed to ensure that SETVAL() is replication safe. If you want to set the SEQUENCE to a smaller number use ALTER SEQUENCE.

If CYCLE is used, first round and then next_value are compared to see if the value is bigger than the current value.

Internally, in the MariaDB server, SETVAL() is used to inform slaves that a SEQUENCE has changed value. The slave may get SETVAL() statements out of order, but this is ok as only the biggest one will have an effect.

SETVAL requires the INSERT privilege.

Examples

SELECT setval(foo, 42);           -- Next nextval will return 43
SELECT setval(foo, 42, true);     -- Same as above
SELECT setval(foo, 42, false);    -- Next nextval will return 42

SETVAL setting higher and lower values on a sequence with an increment of 10:

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|         50 |
+------------+

SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
|            100 |
+----------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        110 |
+------------+

SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
|          NULL |
+---------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        120 |
+------------+

Example demonstrating round:

CREATE OR REPLACE SEQUENCE s1
  START WITH 1
  MINVALUE 1
  MAXVALUE 99
  INCREMENT BY 1 
  CACHE 20 
  CYCLE;

SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
|                   99 |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           1 |
+-------------+

The following statement returns NULL, as the given next_value and round is smaller than the current value.

SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
|                 NULL |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           2 |
+-------------+

Increasing the round from zero to 1 will allow next_value to be returned.

SELECT SETVAL(s1, 99, 1, 1);
+----------------------+
| SETVAL(s1, 99, 1, 1) |
+----------------------+
|                   99 |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           1 |
+-------------+

See Also

JSON_ARRAY_APPEND

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_ARRAY_APPEND(json_doc, path, value[, path, value] ...)

Description

Appends values to the end of the specified arrays within a JSON document, returning the result, or NULL if any of the arguments are NULL.

Evaluation is performed from left to right, with the resulting document from the previous pair becoming the new value against which the next pair is evaluated.

If the json_doc is not a valid JSON document, or if any of the paths are not valid, or contain a * or ** wildcard, an error is returned.

Examples

SET @json = '[1, 2, [3, 4]]';

SELECT JSON_ARRAY_APPEND(@json, '$[0]', 5)
+-------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[0]', 5) |
+-------------------------------------+
| [[1, 5], 2, [3, 4]]                 |
+-------------------------------------+

SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6);
+-------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[1]', 6) |
+-------------------------------------+
| [1, [2, 6], [3, 4]]                 |
+-------------------------------------+

SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7);
+------------------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7) |
+------------------------------------------------+
| [1, [2, 6], [3, 4, 7]]                         |
+------------------------------------------------+

SELECT JSON_ARRAY_APPEND(@json, '$', 5);
+----------------------------------+
| JSON_ARRAY_APPEND(@json, '$', 5) |
+----------------------------------+
| [1, 2, [3, 4], 5]                |
+----------------------------------+

SET @json = '{"A": 1, "B": [2], "C": [3, 4]}';

SELECT JSON_ARRAY_APPEND(@json, '$.B', 5);
+------------------------------------+
| JSON_ARRAY_APPEND(@json, '$.B', 5) |
+------------------------------------+
| {"A": 1, "B": [2, 5], "C": [3, 4]} |
+------------------------------------+

JSON_ARRAY_INSERT

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_ARRAY_INSERT(json_doc, path, value[, path, value] ...)

Description

Inserts a value into a JSON document, returning the modified document, or NULL if any of the arguments are NULL.

Evaluation is performed from left to right, with the resulting document from the previous pair becoming the new value against which the next pair is evaluated.

If the json_doc is not a valid JSON document, or if any of the paths are not valid, or contain a * or ** wildcard, an error is returned.

Examples

SET @json = '[1, 2, [3, 4]]';

SELECT JSON_ARRAY_INSERT(@json, '$[0]', 5);
+-------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[0]', 5) |
+-------------------------------------+
| [5, 1, 2, [3, 4]]                   |
+-------------------------------------+

SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6);
+-------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[1]', 6) |
+-------------------------------------+
| [1, 6, 2, [3, 4]]                   |
+-------------------------------------+

SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7);
+------------------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7) |
+------------------------------------------------+
| [1, 6, 7, 2, [3, 4]]                           |
+------------------------------------------------+

JSON_CONTAINS

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_CONTAINS(json_doc, val[, path])

Description

Returns whether or not the specified value is found in the given JSON document or, optionally, at the specified path within the document. Returns 1 if it does, 0 if not and NULL if any of the arguments are null. An error occurs if the document or path is not valid, or contains the * or ** wildcards.

Examples

SET @json = '{"A": 0, "B": {"C": 1}, "D": 2}';

SELECT JSON_CONTAINS(@json, '2', '$.A');
+----------------------------------+
| JSON_CONTAINS(@json, '2', '$.A') |
+----------------------------------+
|                                0 |
+----------------------------------+

SELECT JSON_CONTAINS(@json, '2', '$.D');
+----------------------------------+
| JSON_CONTAINS(@json, '2', '$.D') |
+----------------------------------+
|                                1 |
+----------------------------------+

SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.A');
+-----------------------------------------+
| JSON_CONTAINS(@json, '{"C": 1}', '$.A') |
+-----------------------------------------+
|                                       0 |
+-----------------------------------------+

SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.B');
+-----------------------------------------+
| JSON_CONTAINS(@json, '{"C": 1}', '$.B') |
+-----------------------------------------+
|                                       1 |
+-----------------------------------------+

JSON_CONTAINS_PATH

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_CONTAINS_PATH(json_doc, return_arg, path[, path] ...)

Description

Indicates whether the given JSON document contains data at the specified path or paths. Returns 1 if it does, 0 if not and NULL if any of the arguments are null.

The return_arg can be one or all:

  • one - Returns 1 if at least one path exists within the JSON document.
  • all - Returns 1 only if all paths exist within the JSON document.

Examples

SET @json = '{"A": 1, "B": [2], "C": [3, 4]}';

SELECT JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D');
+------------------------------------------------+
| JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D') |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+
1 row in set (0.00 sec)

SELECT JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D');
+------------------------------------------------+
| JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D') |
+------------------------------------------------+
|                                              0 |
+------------------------------------------------+

JSON_DEPTH

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_DEPTH(json_doc)

Description

Returns the maximum depth of the given JSON document, or NULL if the argument is null. An error will occur if the argument is an invalid JSON document.

  • Scalar values or empty arrays or objects have a depth of 1.
  • Arrays or objects that are not empty but contain only elements or member values of depth 1 will have a depth of 2.
  • In other cases, the depth will be greater than 2.

Examples

SELECT JSON_DEPTH('[]'), JSON_DEPTH('true'), JSON_DEPTH('{}');
+------------------+--------------------+------------------+
| JSON_DEPTH('[]') | JSON_DEPTH('true') | JSON_DEPTH('{}') |
+------------------+--------------------+------------------+
|                1 |                  1 |                1 |
+------------------+--------------------+------------------+

SELECT JSON_DEPTH('[1, 2, 3]'), JSON_DEPTH('[[], {}, []]');
+-------------------------+----------------------------+
| JSON_DEPTH('[1, 2, 3]') | JSON_DEPTH('[[], {}, []]') |
+-------------------------+----------------------------+
|                       2 |                          2 |
+-------------------------+----------------------------+

SELECT JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]');
+---------------------------------------+
| JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]') |
+---------------------------------------+
|                                     3 |
+---------------------------------------+

JSON_EXISTS

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

Description

Determines whether a specified JSON value exists in the given data. Returns 1 if found, 0 if not, or NULL if any of the inputs were NULL.

Examples

SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2");
+------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2") |
+------------------------------------------------------------+
|                                                          1 |
+------------------------------------------------------------+

SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key3");
+------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key3") |
+------------------------------------------------------------+
|                                                          0 |
+------------------------------------------------------------+

SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[1]");
+---------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[1]") |
+---------------------------------------------------------------+
|                                                             1 |
+---------------------------------------------------------------+

SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[10]");
+----------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}', "$.key2[10]") |
+----------------------------------------------------------------+
|                                                              0 |
+----------------------------------------------------------------+

JSON_EXTRACT

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_EXTRACT(json_doc, path[, path] ...)

Description

Extracts data from a JSON document. The extracted data is selected from the parts matching the path arguments. Returns all matched values; either as a single matched value, or, if the arguments could return multiple values, a result autowrapped as an array in the matching order.

Returns NULL if no paths match or if any of the arguments are NULL.

An error will occur if any path argument is not a valid path, or if the json_doc argument is not a valid JSON document.

The path expression be a JSONPath expression as supported by MariaDB

Examples

SET @json = '[1, 2, [3, 4]]';

SELECT JSON_EXTRACT(@json, '$[1]');
+-----------------------------+
| JSON_EXTRACT(@json, '$[1]') |
+-----------------------------+
| 2                           |
+-----------------------------+

SELECT JSON_EXTRACT(@json, '$[2]');
+-----------------------------+
| JSON_EXTRACT(@json, '$[2]') |
+-----------------------------+
| [3, 4]                      |
+-----------------------------+

SELECT JSON_EXTRACT(@json, '$[2][1]');
+--------------------------------+
| JSON_EXTRACT(@json, '$[2][1]') |
+--------------------------------+
| 4                              |
+--------------------------------+

See Also

JSON_INSERT

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_INSERT(json_doc, path, val[, path, val] ...)

Description

Inserts data into a JSON document, returning the resulting document or NULL if any argument is null.

An error will occur if the JSON document is not invalid, or if any of the paths are invalid or contain a * or ** wildcard.

JSON_INSERT can only insert data while JSON_REPLACE can only update. JSON_SET can update or insert data.

Examples

SET @json = '{ "A": 0, "B": [1, 2]}';

SELECT JSON_INSERT(@json, '$.C', '[3, 4]');
+--------------------------------------+
| JSON_INSERT(@json, '$.C', '[3, 4]')  |
+--------------------------------------+
| { "A": 0, "B": [1, 2], "C":"[3, 4]"} |
+--------------------------------------+

See Also

JSON_KEYS

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_KEYS(json_doc[, path])

Description

Returns the keys as a JSON array from the top-level value of a JSON object or, if the optional path argument is provided, the top-level keys from the path.

Excludes keys from nested sub-objects in the top level value. The resulting array will be empty if the selected object is empty.

Returns NULL if any of the arguments are null, a given path does not locate an object, or if the json_doc argument is not an object.

An error will occur if JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard.

Examples

SELECT JSON_KEYS('{"A": 1, "B": {"C": 2}}');
+--------------------------------------+
| JSON_KEYS('{"A": 1, "B": {"C": 2}}') |
+--------------------------------------+
| ["A", "B"]                           |
+--------------------------------------+

SELECT JSON_KEYS('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C');
+-----------------------------------------------------+
| JSON_KEYS('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C') |
+-----------------------------------------------------+
| ["D"]                                               |
+-----------------------------------------------------+

JSON_LENGTH

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_LENGTH(json_doc[, path])

Description

Returns the length of a JSON document, or, if the optional path argument is given, the length of the value within the document specified by the path.

Returns NULL if any of the arguments argument are null or the path argument does not identify a value in the document.

An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard.

Length will be determined as follow:

  • A scalar's length is always 1.
  • If an array, the number of elements in the array.
  • If an object, the number of members in the object.

The length of nested arrays or objects are not counted.

Examples


JSON_QUERY

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_QUERY(json_doc, path)

Description

Given a JSON document, returns an object or array specified by the path. Returns NULL if not given a valid JSON document, or if there is no match.

Examples

select json_query('{"key1":{"a":1, "b":[1,2]}}', '$.key1');
+-----------------------------------------------------+
| json_query('{"key1":{"a":1, "b":[1,2]}}', '$.key1') |
+-----------------------------------------------------+
| {"a":1, "b":[1,2]}                                  |
+-----------------------------------------------------+

select json_query('{"key1":123, "key1": [1,2,3]}', '$.key1');
+-------------------------------------------------------+
| json_query('{"key1":123, "key1": [1,2,3]}', '$.key1') |
+-------------------------------------------------------+
| [1,2,3]                                               |
+-------------------------------------------------------+

JSON_QUOTE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_QUOTE(json_value)

Description

Quotes a string as a JSON value, usually for producing valid JSON string literals for inclusion in JSON documents. Wraps the string with double quote characters and escapes interior quotes and other special characters, returning a utf8mb4 string.

Returns NULL if the argument is NULL.

Examples

SELECT JSON_QUOTE('A'), JSON_QUOTE("B"), JSON_QUOTE('"C"');
+-----------------+-----------------+-------------------+
| JSON_QUOTE('A') | JSON_QUOTE("B") | JSON_QUOTE('"C"') |
+-----------------+-----------------+-------------------+
| "A"             | "B"             | "\"C\""           |
+-----------------+-----------------+-------------------+

JSON_REMOVE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_REMOVE(json_doc, path[, path] ...)

Description

Removes data from a JSON document returning the result, or NULL if any of the arguments are null. If the element does not exist in the document, no changes are made.

An error will occur if JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard.

Path arguments are evaluated from left to right, with the result from the earlier evaluation being used as the value for the next.

Examples

SELECT JSON_REMOVE('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C');
+-------------------------------------------------------+
| JSON_REMOVE('{"A": 1, "B": 2, "C": {"D": 3}}', '$.C') |
+-------------------------------------------------------+
| {"A": 1, "B": 2}                                      |
+-------------------------------------------------------+

SELECT JSON_REMOVE('["A", "B", ["C", "D"], "E"]', '$[1]');
+----------------------------------------------------+
| JSON_REMOVE('["A", "B", ["C", "D"], "E"]', '$[1]') |
+----------------------------------------------------+
| ["A", ["C", "D"], "E"]                             |
+----------------------------------------------------+

See Also

JSON_REPLACE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_REPLACE(json_doc, path, val[, path, val] ...)

Description

Replaces existing values in a JSON document, returning the result, or NULL if any of the arguments are NULL.

An error will occur if the JSON document is invalid, the path is invalid or if the path contains a * or ** wildcard.

Paths and values are evaluated from left to right, with the result from the earlier evaluation being used as the value for the next.

JSON_REPLACE can only update data, while JSON_INSERT can only insert. JSON_SET can update or insert data.

Examples

SELECT JSON_REPLACE('{ "A": 1, "B": [2, 3]}', '$.B[1]', 4);
+-----------------------------------------------------+
| JSON_REPLACE('{ "A": 1, "B": [2, 3]}', '$.B[1]', 4) |
+-----------------------------------------------------+
| { "A": 1, "B": [2, 4]}                              |
+-----------------------------------------------------+

See Also

JSON_SEARCH

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_SEARCH(json_doc, return_arg, search_str[, escape_char[, path] ...])

Description

Returns the path to the given string within a JSON document, or NULL if any of json_doc, search_str or a path argument is NULL; if the search string is not found, or if no path exists within the document.

A warning will occur if the JSON document is not valid, any of the path arguments are not valid, if return_arg is neither one nor all, or if the escape character is not a constant. NULL will be returned.

return_arg can be one of two values:

  • 'one: Terminates after finding the first match, so will return one path string. If there is more than one match, it is undefined which is considered first.
  • all: Returns all matching path strings, without duplicates. Multiple strings are autowrapped as an array. The order is undefined.

Examples

SET @json = '["A", [{"B": "1"}], {"C":"AB"}, {"D":"BC"}]';

SELECT JSON_SEARCH(@json, 'one', 'AB');
+---------------------------------+
| JSON_SEARCH(@json, 'one', 'AB') |
+---------------------------------+
| "$[2].C"                        |
+---------------------------------+

JSON_TYPE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_TYPE(json_val)

Description

Returns the type of a JSON value (as a string), or NULL if the argument is null.

An error will occur if the argument is an invalid JSON value.

The following is a complete list of the possible return types:

Return typeValueExample
ARRAYJSON array[1, 2, {"key": "value"}]
OBJECTJSON object{"key":"value"}
BOOLEANJSON true/false literalstrue, false
DOUBLEA number with at least one floating point decimal.1.2
INTEGERA number without a floating point decimal.1
NULLJSON null literal (this is returned as a string, not to be confused with the SQL NULL value!)null
STRINGJSON String"a sample string"

Examples

SELECT JSON_TYPE('{"A": 1, "B": 2, "C": 3}');
+---------------------------------------+
| JSON_TYPE('{"A": 1, "B": 2, "C": 3}') |
+---------------------------------------+
| OBJECT                                |
+---------------------------------------+

JSON_UNQUOTE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_UNQUOTE(val)

Description

Unquotes a JSON value, returning a string, or NULL if the argument is null.

An error will occur if the given value begins and ends with double quotes and is an invalid JSON string literal.

If the given value is not a JSON string, value is passed through unmodified.

Certain character sequences have special meanings within a string. Usually, a backslash is ignored, but the escape sequences in the table below are recognised by MariaDB, unless the SQL Mode is set to NO_BACKSLASH_ESCAPES SQL.

Escape sequenceCharacter
\"Double quote (")
\bBackslash
\fFormfeed
\nNewline (linefeed)
\rCarriage return
\tTab
\\Backslash (\)
\uXXXXUTF-8 bytes for Unicode value XXXX

Examples

SELECT JSON_UNQUOTE('"Monty"');
+-------------------------+
| JSON_UNQUOTE('"Monty"') |
+-------------------------+
| Monty                   |
+-------------------------+

With the default SQL Mode:

SELECT JSON_UNQUOTE('Si\bng\ting');
+-----------------------------+
| JSON_UNQUOTE('Si\bng\ting') |
+-----------------------------+
| Sng	ing                   |
+-----------------------------+

Setting NO_BACKSLASH_ESCAPES:

SET @@sql_mode = 'NO_BACKSLASH_ESCAPES';

SELECT JSON_UNQUOTE('Si\bng\ting');
+-----------------------------+
| JSON_UNQUOTE('Si\bng\ting') |
+-----------------------------+
| Si\bng\ting                 |
+-----------------------------+

JSON_VALID

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_VALID(value)

Description

Indicates whether the given value is a valid JSON document or not. Returns 1 if valid, 0 if not, and NULL if the argument is NULL.

From MariaDB 10.4.3, the JSON_VALID function is automatically used as a CHECK constraint for the JSON data type alias in order to ensure that a valid json document is inserted.

Examples

SELECT JSON_VALID('{"id": 1, "name": "Monty"}');
+------------------------------------------+
| JSON_VALID('{"id": 1, "name": "Monty"}') |
+------------------------------------------+
|                                        1 |
+------------------------------------------+

SELECT JSON_VALID('{"id": 1, "name": "Monty", "oddfield"}');
+------------------------------------------------------+
| JSON_VALID('{"id": 1, "name": "Monty", "oddfield"}') |
+------------------------------------------------------+
|                                                    0 |
+------------------------------------------------------+

See Also

JSON_VALUE

MariaDB starting with 10.2.3

JSON functions were added in MariaDB 10.2.3.

Syntax

JSON_VALUE(json_doc, path)

Description

Given a JSON document, returns the scalar specified by the path. Returns NULL if not given a valid JSON document, or if there is no match.

Examples

select json_value('{"key1":123}', '$.key1');
+--------------------------------------+
| json_value('{"key1":123}', '$.key1') |
+--------------------------------------+
| 123                                  |
+--------------------------------------+

select json_value('{"key1": [1,2,3], "key1":123}', '$.key1');
+-------------------------------------------------------+
| json_value('{"key1": [1,2,3], "key1":123}', '$.key1') |
+-------------------------------------------------------+
| 123                                                   |
+-------------------------------------------------------+

DENSE_RANK

MariaDB starting with 10.2

The DENSE_RANK() function was first introduced with window functions in MariaDB 10.2.0.

Syntax

DENSE_RANK() OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

DENSE_RANK() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. Unlike the RANK() function, there are no skipped values if the preceding results are identical. It is also similar to the ROW_NUMBER() function except that in that function, identical values will receive a different row number for each result.

Examples

The distinction between DENSE_RANK(), RANK() and ROW_NUMBER():

CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10));

INSERT INTO student VALUES 
  ('Maths', 60, 'Thulile'),
  ('Maths', 60, 'Pritha'),
  ('Maths', 70, 'Voitto'),
  ('Maths', 55, 'Chun'),
  ('Biology', 60, 'Bilal'),
   ('Biology', 70, 'Roger');

SELECT 
  RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, 
  DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, 
  ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, 
  course, mark, name 
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course  | mark | name    |
+------+------------+---------+---------+------+---------+
|    1 |          1 |       1 | Biology |   70 | Roger   |
|    2 |          2 |       2 | Biology |   60 | Bilal   |
|    1 |          1 |       1 | Maths   |   70 | Voitto  |
|    2 |          2 |       2 | Maths   |   60 | Thulile |
|    2 |          2 |       3 | Maths   |   60 | Pritha  |
|    4 |          3 |       4 | Maths   |   55 | Chun    |
+------+------------+---------+---------+------+---------+

See Also

FIRST_VALUE

MariaDB starting with 10.2.2

The FIRST_VALUE() function was first introduced with other window functions in MariaDB 10.2.

Syntax

FIRST_VALUE(expr) OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

FIRST_VALUE returns the first result from an ordered set, or NULL if no such result exists.

Examples

CREATE TABLE t1 (
  pk int primary key,
  a int,
  b int,
  c char(10),
  d decimal(10, 3),
  e real
);

INSERT INTO t1 VALUES
( 1, 0, 1,    'one',    0.1,  0.001),
( 2, 0, 2,    'two',    0.2,  0.002),
( 3, 0, 3,    'three',  0.3,  0.003),
( 4, 1, 2,    'three',  0.4,  0.004),
( 5, 1, 1,    'two',    0.5,  0.005),
( 6, 1, 1,    'one',    0.6,  0.006),
( 7, 2, NULL, 'n_one',  0.5,  0.007),
( 8, 2, 1,    'n_two',  NULL, 0.008),
( 9, 2, 2,    NULL,     0.7,  0.009),
(10, 2, 0,    'n_four', 0.8,  0.010),
(11, 2, 10,   NULL,     0.9,  NULL);

SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
           LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
           FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
           LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;

+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 |         1 |       11 |         11 |        11 |
| 10 |         1 |       10 |         11 |        10 |
|  9 |         1 |        9 |         11 |         9 |
|  8 |         1 |        8 |         11 |         8 |
|  7 |         1 |        7 |         11 |         7 |
|  6 |         1 |        6 |         11 |         6 |
|  5 |         1 |        5 |         11 |         5 |
|  4 |         1 |        4 |         11 |         4 |
|  3 |         1 |        3 |         11 |         3 |
|  2 |         1 |        2 |         11 |         2 |
|  1 |         1 |        1 |         11 |         1 |
+----+-----------+----------+------------+-----------+
CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);

SELECT i,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f
FROM t1;

+------+------+------+--------+--------+--------+--------+--------+--------+
| i    | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
|    1 |    1 |    2 |      1 |      2 |   NULL |   NULL |      2 |      3 |
|    2 |    2 |    3 |      1 |      3 |      1 |      1 |      3 |      4 |
|    3 |    3 |    4 |      2 |      4 |      1 |      2 |      4 |      5 |
|    4 |    4 |    5 |      3 |      5 |      2 |      3 |      5 |      6 |
|    5 |    5 |    6 |      4 |      6 |      3 |      4 |      6 |      7 |
|    6 |    6 |    7 |      5 |      7 |      4 |      5 |      7 |      8 |
|    7 |    7 |    8 |      6 |      8 |      5 |      6 |      8 |      9 |
|    8 |    8 |    9 |      7 |      9 |      6 |      7 |      9 |     10 |
|    9 |    9 |   10 |      8 |     10 |      7 |      8 |     10 |     10 |
|   10 |   10 |   10 |      9 |     10 |      8 |      9 |   NULL |   NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+

See Also

LAG

MariaDB starting with 10.2.2

The LAG() function was first introduced with other window functions in MariaDB 10.2.

Syntax

LAG (expr[, offset]) OVER ( 
  [ PARTITION BY partition_expression ] 
  < ORDER BY order_list >
)

Description

The LAG function accesses data from a previous row according to the ORDER BY clause without the need for a self-join. The specific row is determined by the offset (default 1), which specifies the number of rows behind the current row to use. An offset of 0 is the current row.

Examples

CREATE TABLE t1 (pk int primary key, a int, b int, c char(10), d decimal(10, 3), e real);

INSERT INTO t1 VALUES
 ( 1, 0, 1,    'one',    0.1,  0.001),
 ( 2, 0, 2,    'two',    0.2,  0.002),
 ( 3, 0, 3,    'three',  0.3,  0.003),
 ( 4, 1, 2,    'three',  0.4,  0.004),
 ( 5, 1, 1,    'two',    0.5,  0.005),
 ( 6, 1, 1,    'one',    0.6,  0.006),
 ( 7, 2, NULL, 'n_one',  0.5,  0.007),
 ( 8, 2, 1,    'n_two',  NULL, 0.008),
 ( 9, 2, 2,    NULL,     0.7,  0.009),
 (10, 2, 0,    'n_four', 0.8,  0.010),
 (11, 2, 10,   NULL,     0.9,  NULL);

SELECT pk, LAG(pk) OVER (ORDER BY pk) AS l,
  LAG(pk,1) OVER (ORDER BY pk) AS l1,
  LAG(pk,2) OVER (ORDER BY pk) AS l2,
  LAG(pk,0) OVER (ORDER BY pk) AS l0,
  LAG(pk,-1) OVER (ORDER BY pk) AS lm1,
  LAG(pk,-2) OVER (ORDER BY pk) AS lm2 
FROM t1;
+----+------+------+------+------+------+------+
| pk | l    | l1   | l2   | l0   | lm1  | lm2  |
+----+------+------+------+------+------+------+
|  1 | NULL | NULL | NULL |    1 |    2 |    3 |
|  2 |    1 |    1 | NULL |    2 |    3 |    4 |
|  3 |    2 |    2 |    1 |    3 |    4 |    5 |
|  4 |    3 |    3 |    2 |    4 |    5 |    6 |
|  5 |    4 |    4 |    3 |    5 |    6 |    7 |
|  6 |    5 |    5 |    4 |    6 |    7 |    8 |
|  7 |    6 |    6 |    5 |    7 |    8 |    9 |
|  8 |    7 |    7 |    6 |    8 |    9 |   10 |
|  9 |    8 |    8 |    7 |    9 |   10 |   11 |
| 10 |    9 |    9 |    8 |   10 |   11 | NULL |
| 11 |   10 |   10 |    9 |   11 | NULL | NULL |
+----+------+------+------+------+------+------+

See Also

  • LEAD - Window function to access a following row

MEDIAN

MariaDB starting with 10.3.3

The MEDIAN() window function was first introduced with in MariaDB 10.3.3.

Syntax

MEDIAN(median expression) OVER (
  [ PARTITION BY partition_expression ] 
)

Description

MEDIAN() is a window function that returns the median value of a range of values.

It is a specific case of PERCENTILE_CONT, with an argument of 0.5 and the ORDER BY column the one in MEDIAN's argument.

MEDIAN(<median-arg>) OVER ( [ PARTITION BY partition_expression] )

Is equivalent to:

PERCENTILE_CONT(0.5) WITHIN 
  GROUP (ORDER BY <median-arg>) OVER ( [ PARTITION BY partition_expression ])

Examples

CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT);

INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);

SELECT name, median(star_rating) OVER (PARTITION BY name) FROM book_rating;
+-----------------------+----------------------------------------------+
| name                  | median(star_rating) OVER (PARTITION BY name) |
+-----------------------+----------------------------------------------+
| Lord of the Ladybirds |                                 4.0000000000 |
| Lord of the Ladybirds |                                 4.0000000000 |
| Lady of the Flies     |                                 2.0000000000 |
| Lady of the Flies     |                                 2.0000000000 |
| Lady of the Flies     |                                 2.0000000000 |
+-----------------------+----------------------------------------------+

See Also

NTILE

MariaDB starting with 10.2

The NTILE() function was first introduced with window functions in MariaDB 10.2.0.

Syntax

NTILE (expr) OVER ( 
  [ PARTITION BY partition_expression ] 
  [ ORDER BY order_list ]
)

Description

NTILE() is a window function that returns an integer indicating which group a given row falls into. The number of groups is specified in the argument (expr), starting at one. Ordered rows in the partition are divided into the specified number of groups with as equal a size as possible.

Examples

create table t1 (
    pk int primary key,
    a int,
    b int
  );

insert into t1 values
    (11 , 0, 10),
    (12 , 0, 10),
    (13 , 1, 10),
    (14 , 1, 10),
    (18 , 2, 10),
    (15 , 2, 20),
    (16 , 2, 20),
    (17 , 2, 20),
    (19 , 4, 20),
    (20 , 4, 20);

select pk, a, b,
    ntile(1) over (order by pk)
  from t1;
+----+------+------+-----------------------------+
| pk | a    | b    | ntile(1) over (order by pk) |
+----+------+------+-----------------------------+
| 11 |    0 |   10 |                           1 |
| 12 |    0 |   10 |                           1 |
| 13 |    1 |   10 |                           1 |
| 14 |    1 |   10 |                           1 |
| 15 |    2 |   20 |                           1 |
| 16 |    2 |   20 |                           1 |
| 17 |    2 |   20 |                           1 |
| 18 |    2 |   10 |                           1 |
| 19 |    4 |   20 |                           1 |
| 20 |    4 |   20 |                           1 |
+----+------+------+-----------------------------+

select pk, a, b,
    ntile(4) over (order by pk)
 from t1;
+----+------+------+-----------------------------+
| pk | a    | b    | ntile(4) over (order by pk) |
+----+------+------+-----------------------------+
| 11 |    0 |   10 |                           1 |
| 12 |    0 |   10 |                           1 |
| 13 |    1 |   10 |                           1 |
| 14 |    1 |   10 |                           2 |
| 15 |    2 |   20 |                           2 |
| 16 |    2 |   20 |                           2 |
| 17 |    2 |   20 |                           3 |
| 18 |    2 |   10 |                           3 |
| 19 |    4 |   20 |                           4 |
| 20 |    4 |   20 |                           4 |
+----+------+------+-----------------------------+

PERCENT_RANK

MariaDB starting with 10.2

The PERCENT_RANK() function was first introduced with window functions in MariaDB 10.2.0.

Syntax

PERCENT_RANK() OVER (
  [ PARTITION BY partition_expression ] 
  [ ORDER BY order_list ]
)

Description

PERCENT_RANK() is a window function that returns the relative percent rank of a given row. The following formula is used to calculate the percent rank:

(rank - 1) / (number of rows in the window or partition - 1)

Examples

create table t1 (
  pk int primary key,
  a int,
  b int
);


insert into t1 values
( 1 , 0, 10),
( 2 , 0, 10),
( 3 , 1, 10),
( 4 , 1, 10),
( 8 , 2, 10),
( 5 , 2, 20),
( 6 , 2, 20),
( 7 , 2, 20),
( 9 , 4, 20),
(10 , 4, 20);

select pk, a, b,
    rank() over (order by a) as rank,
    percent_rank() over (order by a) as pct_rank,
    cume_dist() over (order by a) as cume_dist
from t1;
+----+------+------+------+--------------+--------------+
| pk | a    | b    | rank | pct_rank     | cume_dist    |
+----+------+------+------+--------------+--------------+
|  1 |    0 |   10 |    1 | 0.0000000000 | 0.2000000000 |
|  2 |    0 |   10 |    1 | 0.0000000000 | 0.2000000000 |
|  3 |    1 |   10 |    3 | 0.2222222222 | 0.4000000000 |
|  4 |    1 |   10 |    3 | 0.2222222222 | 0.4000000000 |
|  5 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  6 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  7 |    2 |   20 |    5 | 0.4444444444 | 0.8000000000 |
|  8 |    2 |   10 |    5 | 0.4444444444 | 0.8000000000 |
|  9 |    4 |   20 |    9 | 0.8888888889 | 1.0000000000 |
| 10 |    4 |   20 |    9 | 0.8888888889 | 1.0000000000 |
+----+------+------+------+--------------+--------------+

select pk, a, b,
       percent_rank() over (order by pk) as pct_rank,
       cume_dist() over (order by pk) as cume_dist
from t1 order by pk;
+----+------+------+--------------+--------------+
| pk | a    | b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 0.1000000000 |
|  2 |    0 |   10 | 0.1111111111 | 0.2000000000 |
|  3 |    1 |   10 | 0.2222222222 | 0.3000000000 |
|  4 |    1 |   10 | 0.3333333333 | 0.4000000000 |
|  5 |    2 |   20 | 0.4444444444 | 0.5000000000 |
|  6 |    2 |   20 | 0.5555555556 | 0.6000000000 |
|  7 |    2 |   20 | 0.6666666667 | 0.7000000000 |
|  8 |    2 |   10 | 0.7777777778 | 0.8000000000 |
|  9 |    4 |   20 | 0.8888888889 | 0.9000000000 |
| 10 |    4 |   20 | 1.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

select pk, a, b,
        percent_rank() over (partition by a order by a) as pct_rank,
        cume_dist() over (partition by a order by a) as cume_dist
from t1;
+----+------+------+--------------+--------------+
| pk | a    | b    | pct_rank     | cume_dist    |
+----+------+------+--------------+--------------+
|  1 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  2 |    0 |   10 | 0.0000000000 | 1.0000000000 |
|  3 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  4 |    1 |   10 | 0.0000000000 | 1.0000000000 |
|  5 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  6 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  7 |    2 |   20 | 0.0000000000 | 1.0000000000 |
|  8 |    2 |   10 | 0.0000000000 | 1.0000000000 |
|  9 |    4 |   20 | 0.0000000000 | 1.0000000000 |
| 10 |    4 |   20 | 0.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+

See Also

PERCENTILE_DISC

MariaDB starting with 10.3.3

The PERCENTILE_DISC() window function was first introduced with in MariaDB 10.3.3.

Syntax

Description

PERCENTILE_DISC() (standing for discrete percentile) is a window function which returns the first value in the set whose ordered position is the same or more than the specified fraction.

Essentially, the following process is followed to find the value to return:

  • Get the number of rows in the partition.
  • Walk through the partition, in order, until finding the the first row with CUME_DIST() >= function_argument.

Examples

CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT);

INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);

SELECT name, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY star_rating)
  OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name                  | pc   |
+-----------------------+------+
| Lord of the Ladybirds |    3 |
| Lord of the Ladybirds |    3 |
| Lady of the Flies     |    2 |
| Lady of the Flies     |    2 |
| Lady of the Flies     |    2 |
+-----------------------+------+
5 rows in set (0.000 sec)

SELECT name, PERCENTILE_DISC(0) WITHIN GROUP (ORDER BY star_rating) 
 OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name                  | pc   |
+-----------------------+------+
| Lord of the Ladybirds |    3 |
| Lord of the Ladybirds |    3 |
| Lady of the Flies     |    1 |
| Lady of the Flies     |    1 |
| Lady of the Flies     |    1 |
+-----------------------+------+
5 rows in set (0.000 sec)

SELECT name, PERCENTILE_DISC(1) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name                  | pc   |
+-----------------------+------+
| Lord of the Ladybirds |    5 |
| Lord of the Ladybirds |    5 |
| Lady of the Flies     |    5 |
| Lady of the Flies     |    5 |
| Lady of the Flies     |    5 |
+-----------------------+------+
5 rows in set (0.000 sec)

SELECT name, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name                  | pc   |
+-----------------------+------+
| Lord of the Ladybirds |    5 |
| Lord of the Ladybirds |    5 |
| Lady of the Flies     |    2 |
| Lady of the Flies     |    2 |
| Lady of the Flies     |    2 |
+-----------------------+------

See Also

PERCENTILE_CONT

MariaDB starting with 10.3.3

The PERCENTILE_CONT() window function was first introduced with in MariaDB 10.3.3.

Syntax

Description

PERCENTILE_CONT() (standing for continuous percentile) is a window function which returns a value which corresponds to the given fraction in the sort order. If required, it will interpolate between adjacent input items.

Essentially, the following process is followed to find the value to return:

  • Get the number of rows in the partition, denoted by N
  • RN = p*(N-1), where p denotes the argument to the PERCENTILE_CONT function
  • calculate the FRN(floor row number) and CRN(column row number for the group( FRN= floor(RN) and CRN = ceil(RN))
  • look up rows FRN and CRN
  • If (CRN = FRN = RN) then the result is (value of expression from row at RN)
  • Otherwise the result is
  • (CRN - RN) * (value of expression for row at FRN) +
  • (RN - FRN) * (value of expression for row at CRN)

The MEDIAN function is a specific case of PERCENTILE_CONT, equivalent to PERCENTILE_CONT(0.5).

Examples

CREATE TABLE book_rating (name CHAR(30), star_rating TINYINT);

INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds', 3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);

SELECT name, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc 
  FROM book_rating;
+-----------------------+--------------+
| name                  | pc           |
+-----------------------+--------------+
| Lord of the Ladybirds | 4.0000000000 |
| Lord of the Ladybirds | 4.0000000000 |
| Lady of the Flies     | 2.0000000000 |
| Lady of the Flies     | 2.0000000000 |
| Lady of the Flies     | 2.0000000000 |
+-----------------------+--------------+

SELECT name, PERCENTILE_CONT(1) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc 
  FROM book_rating;
+-----------------------+--------------+
| name                  | pc           |
+-----------------------+--------------+
| Lord of the Ladybirds | 5.0000000000 |
| Lord of the Ladybirds | 5.0000000000 |
| Lady of the Flies     | 5.0000000000 |
| Lady of the Flies     | 5.0000000000 |
| Lady of the Flies     | 5.0000000000 |
+-----------------------+--------------+

SELECT name, PERCENTILE_CONT(0) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc 
  FROM book_rating;
+-----------------------+--------------+
| name                  | pc           |
+-----------------------+--------------+
| Lord of the Ladybirds | 3.0000000000 |
| Lord of the Ladybirds | 3.0000000000 |
| Lady of the Flies     | 1.0000000000 |
| Lady of the Flies     | 1.0000000000 |
| Lady of the Flies     | 1.0000000000 |
+-----------------------+--------------+

SELECT name, PERCENTILE_CONT(0.6) WITHIN GROUP (ORDER BY star_rating) 
  OVER (PARTITION BY name) AS pc 
  FROM book_rating;
+-----------------------+--------------+
| name                  | pc           |
+-----------------------+--------------+
| Lord of the Ladybirds | 4.2000000000 |
| Lord of the Ladybirds | 4.2000000000 |
| Lady of the Flies     | 2.6000000000 |
| Lady of the Flies     | 2.6000000000 |
| Lady of the Flies     | 2.6000000000 |
+-----------------------+--------------+

See Also

  • MEDIAN() - a special case of PERCENTILE_CONT equivalent to PERCENTILE_CONT(0.5)

RANK

MariaDB starting with 10.2

The RANK() function was first introduced with window functions in MariaDB 10.2.0.

Syntax

RANK() OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

RANK() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving the same result. It is similar to the ROW_NUMBER() function except that in that function, identical values will receive a different row number for each result.

Examples

The distinction between DENSE_RANK(), RANK() and ROW_NUMBER():

CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10));

INSERT INTO student VALUES 
  ('Maths', 60, 'Thulile'),
  ('Maths', 60, 'Pritha'),
  ('Maths', 70, 'Voitto'),
  ('Maths', 55, 'Chun'),
  ('Biology', 60, 'Bilal'),
   ('Biology', 70, 'Roger');

SELECT 
  RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, 
  DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, 
  ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, 
  course, mark, name 
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course  | mark | name    |
+------+------------+---------+---------+------+---------+
|    1 |          1 |       1 | Biology |   70 | Roger   |
|    2 |          2 |       2 | Biology |   60 | Bilal   |
|    1 |          1 |       1 | Maths   |   70 | Voitto  |
|    2 |          2 |       2 | Maths   |   60 | Thulile |
|    2 |          2 |       3 | Maths   |   60 | Pritha  |
|    4 |          3 |       4 | Maths   |   55 | Chun    |
+------+------------+---------+---------+------+---------+

See Also

ROW_NUMBER

MariaDB starting with 10.2

ROW_NUMBER() was first introduced with window functions in MariaDB 10.2.0.

Syntax

ROW_NUMBER() OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

ROW_NUMBER() is a window function that displays the number of a given row, starting at one and following the ORDER BY sequence of the window function, with identical values receiving different row numbers. It is similar to the RANK() and DENSE_RANK() functions except that in that function, identical values will receive the same rank for each result.

Examples

The distinction between DENSE_RANK(), RANK() and ROW_NUMBER():

CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10));

INSERT INTO student VALUES 
  ('Maths', 60, 'Thulile'),
  ('Maths', 60, 'Pritha'),
  ('Maths', 70, 'Voitto'),
  ('Maths', 55, 'Chun'),
  ('Biology', 60, 'Bilal'),
   ('Biology', 70, 'Roger');

SELECT 
  RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, 
  DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, 
  ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, 
  course, mark, name 
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course  | mark | name    |
+------+------------+---------+---------+------+---------+
|    1 |          1 |       1 | Biology |   70 | Roger   |
|    2 |          2 |       2 | Biology |   60 | Bilal   |
|    1 |          1 |       1 | Maths   |   70 | Voitto  |
|    2 |          2 |       2 | Maths   |   60 | Thulile |
|    2 |          2 |       3 | Maths   |   60 | Pritha  |
|    4 |          3 |       4 | Maths   |   55 | Chun    |
+------+------------+---------+---------+------+---------+

See Also

SPIDER_BG_DIRECT_SQL

Syntax

SPIDER_BG_DIRECT_SQL('sql', 'tmp_table_list', 'parameters')

Description

Executes the given SQL statement in the background on the remote server, as defined in the parameters listing. If the query returns a result-set, it sttores the results in the given temporary table. When the given SQL statement executes successfully, this function returns the number of called UDF's. It returns 0 when the given SQL statement fails.

This function is a UDF installed with the Spider storage engine.

Examples

SELECT SPIDER_BG_DIRECT_SQL('SELECT * FROM example_table',  '', 
   'srv "node1", port "8607"') AS "Direct Query";
+--------------+
| Direct Query | 
+--------------+
|            1 |
+--------------+

Parameters

error_rw_mode

  • Description: Returns empty results on network error.
    • 0 : Return error on getting network error.
    • 1: Return 0 records on getting network error.
  • Default Table Value: 0
  • DSN Parameter Name: erwm

See also

SPIDER_COPY_TABLES

Syntax

SPIDER_COPY_TABLES(spider_table_name, 
  source_link_id, destination_link_id_list [,parameters])

Description

A UDF installed with the Spider Storage Engine, this function copies table data from source_link_id to destination_link_id_list. The service does not need to be stopped in order to copy.

If the Spider table is partitioned, the name must be of the format table_name#P#partition_name. The partition name can be viewed in the mysql.spider_tables table, for example:

SELECT table_name FROM mysql.spider_tables;
+-------------+
| table_name  |
+-------------+
| spt_a#P#pt1 |
| spt_a#P#pt2 |
| spt_a#P#pt3 |
+-------------+

Returns 1 if the data was copied successfully, or 0 if copying the data failed.

SPIDER_DIRECT_SQL

Syntax

SPIDER_DIRECT_SQL('sql', 'tmp_table_list', 'parameters')

Description

A UDF installed with the Spider Storage Engine, this function is used to execute the SQL string sql on the remote server, as defined in parameters. If any resultsets are returned, they are stored in the tmp_table_list.

The function returns 1 if the SQL executes successfully, or 0 if it fails.

Examples

SELECT SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv "node1", port "8607"');
+----------------------------------------------------------------------+
| SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv "node1", port "8607"') |
+----------------------------------------------------------------------+
|                                                                    1 |
+----------------------------------------------------------------------+

See also

COLUMN_ADD

Syntax

COLUMN_ADD(dyncol_blob, column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_ADD(dyncol_blob, column_name, value [as type], [column_name, value [as type]]...);

Description

Adds or updates dynamic columns.

  • dyncol_blob must be either a valid dynamic columns blob (for example, COLUMN_CREATE returns such blob), or an empty string.
  • column_name specifies the name of the column to be added. If dyncol_blob already has a column with this name, it will be overwritten.
  • value specifies the new value for the column. Passing a NULL value will cause the column to be deleted.
  • as type is optional. See #datatypes section for a discussion about types.

The return value is a dynamic column blob after the modifications.

Examples

UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob, "column_name", "value") WHERE id=1;

Note: COLUMN_ADD() is a regular function (just like CONCAT()), hence, in order to update the value in the table you have to use the UPDATE ... SET dynamic_col=COLUMN_ADD(dynamic_col, ....) pattern.

COLUMN_CREATE

Syntax

COLUMN_CREATE(column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_CREATE(column_name, value [as type], [column_name, value [as type]]...);

Description

Returns a dynamic columns blob that stores the specified columns with values.

The return value is suitable for

  • storing in a table
  • further modification with other dynamic columns functions

The as type part allows one to specify the value type. In most cases, this is redundant because MariaDB will be able to deduce the type of the value. Explicit type specification may be needed when the type of the value is not apparent. For example, a literal '2012-12-01' has a CHAR type by default, one will need to specify '2012-12-01' AS DATE to have it stored as a date. See Dynamic Columns:Datatypes for further details.

Examples

INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE("column_name", "value");

COLUMN_GET

Syntax

COLUMN_GET(dyncol_blob, column_nr as type);
COLUMN_GET(dyncol_blob, column_name as type);

Description

Gets the value of a dynamic column by its name. If no column with the given name exists, NULL will be returned.

column_name as type requires that one specify the datatype of the dynamic column they are reading.

This may seem counter-intuitive: why would one need to specify which datatype they're retrieving? Can't the dynamic columns system figure the datatype from the data being stored?

The answer is: SQL is a statically-typed language. The SQL interpreter needs to know the datatypes of all expressions before the query is run (for example, when one is using prepared statements and runs "select COLUMN_GET(...)", the prepared statement API requires the server to inform the client about the datatype of the column being read before the query is executed and the server can see what datatype the column actually has).

Lengths

If you're running queries like:

SELECT COLUMN_GET(blob, 'colname' as CHAR) ...

without specifying a maximum length (i.e. using as CHAR, not as CHAR(n)), MariaDB will report the maximum length of the resultset column to be 53,6870,911 for MariaDB 5.3-10.0.0 and 16,777,216 for MariaDB 10.0.1+. This may cause excessive memory usage in some client libraries, because they try to pre-allocate a buffer of maximum resultset width. To avoid this problem, use CHAR(n) whenever you're using COLUMN_GET in the select list.

See Dynamic Columns:Datatypes for more information about datatypes.

COLUMN_JSON

Syntax

COLUMN_JSON(dyncol_blob)

Description

Returns a JSON representation of data in dyncol_blob. Can also be used to display nested columns. See dynamic columns for more information.

Example

select item_name, COLUMN_JSON(dynamic_cols) from assets;
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"black","warranty":"3 years"} |
+-----------------+----------------------------------------+

Limitation: COLUMN_JSON will decode nested dynamic columns at a nesting level of not more than 10 levels deep. Dynamic columns that are nested deeper than 10 levels will be shown as BINARY string, without encoding.